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Ask Slashdot: Building a Large Email Service

Cliff posted more than 15 years ago | from the built-it-and-they-will-come dept.

Linux 484

Rewd asks: "I'm looking at implementing a large scale email server (cluster) to handle POP3 and IMAP4 for about 25000 people, including a lot of attachments. I'd like to go for an Open Source solution, but a lot of people around here want to go for Microsoft Exchange on NT. Has anyone here successfully built anything like this? Can you recommend any combinations and components which are particularly efficent, capable, secure and reliable?"

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Netscape Messaging Server (0)

Anonymous Coward | more than 15 years ago | (#1775833)

Use Netscape Messaging Server. It's not
open source, but it's the best IMAP server
on the planet. Plus, it runs on Linux.

Re:Not Netscape... (0)

Anonymous Coward | more than 15 years ago | (#1775834)

You are obviously not totally familiar with
Netscape's messaging systems. It uses an
LDAP directory for all the addresses and
aliases, which is the absolute ideal scenario
in this day and age.

You'd be crazy not to use open source. (0)

Anonymous Coward | more than 15 years ago | (#1775835)

In supporting 25000 users you want to be sure
you can address whatever problems may present

The NT solution involves pulling out your
credit card and maybe MS can fix it for you.

Open source means a fix might already be
findable on dejanews.

25000 on NT? (0)

Anonymous Coward | more than 15 years ago | (#1775836)

Forget it, not even worth buying that many licenses on exchange. It'll end up crashing just like every other piece of microsoft software.

FreeBSD can handle that with no problem, regardless of the size of messages.

Just make sure you use SCSI! =)

Re:Not Netscape... (0)

Anonymous Coward | more than 15 years ago | (#1775837)

I'm not talking about how it stores the aliases, but for example, if you want to change your aliases in sendmail you just run new aliases, it processes everything and it goes pretty fast. In netscape you run the equivalent and it will process each entry one at a time. It can make a process that might take a few minutes take hours and hours.

General impressions of Netscape's stuff is that it tries to make itself easy to administer, etc, but sacrifices some functionality in the process.

Big Box (0)

Anonymous Coward | more than 15 years ago | (#1775838)

Yeah... simplicity says you want the big box approach... Personal preference lies with getting a Killer Alpha (the new Compaq XP1000 with a 600 MHz 21264 Alpha). 90-100 Gigs of RAID 5. A far inferior Alpha to that runs e-mail for 20000 on this college campus, and everyone here runs pine on the server (more overhead).

Not Open Source, but the Tru64 License is going to be a lot cheaper than the Microsoft fiasco.

I had Exchange to work well (0)

Anonymous Coward | more than 15 years ago | (#1775839)

I was the Exchange admin of a company with 10,000 Exchange users on NT boxes. No real problem. Handled the load just fine. 10,000 users on 4 Pentium 266's. No sweat.

Re:25000 on NT? (0)

Anonymous Coward | more than 15 years ago | (#1775840)

Unqualified flamebait.

Perhaps a sun? (0)

Anonymous Coward | more than 15 years ago | (#1775841)

Actually, I'd suggest going with a Sun. Alphas are very good at heavy duty processing but they don't have as much strength in the realm of I/O. Sun's are weaker processors, but they have great I/O. Since it is mass processing of mail that we're talking about here, the I/O is the important part.

Re:Not Netscape... (0)

Anonymous Coward | more than 15 years ago | (#1775842)

First, sendmail handles only SMTP, not POP or
IMAP. Plus, unless you completely customize it,
sendmail will store mail in one giant file per user,
making random acess via IMAP painfully slow.

Second, there are many things Netscape Messaging
Server can do with aliases that sendmail cannot.
For example, dynamic LDAP aliases. So you could,
for example, have an alias Hawaiian users that
automatically matches anyone with an 808 area

Plus, Netscape Messaging Server 4.1 comes with
a wicked cool HTML mail interface a la Hotmail,
but much better.

Large E-mail installations (0)

Anonymous Coward | more than 15 years ago | (#1775843)

I would check out Cyrus IMAP. It has been fairly well tested in large environments (Colleges and such). It also has an active mail list that is responsive to questions such as this.

current beta is 1.6.1, not sure about the current stable release.

It has many options and allows you to have mail accounts that are not mapped to a real account on the box.

Sorry this is under Anonymous Coward, but when I went to sign up for an account netscape hung...

Exchange: it's not just for email (0)

Anonymous Coward | more than 15 years ago | (#1775844)

We had a similar discussion in my workplace (specifically Exchange vs. QMail). We're a small company, so volume wasn't an issue. What finally tipped the scales in the favor of Exchange was that it isn't just a POP3 server - when used with Outlook and Exchange on the desktop, it lets you do nifty things like share address books, schedule meetings that are automatically entered into people's calendars, and other things that management types like.

If the people arguing for Exchange want these features, you're going to have exchange, 'cause there just isn't an open-source solution (at least, not one that I'm aware of) that integrates email with scheduling and addressbook functions into one tidy package.

Re:I no had English to work well (0)

Anonymous Coward | more than 15 years ago | (#1775845)

No one used the mail system did they?
No attachments?


many rebootparties for the NT's (0)

Anonymous Coward | more than 15 years ago | (#1775846)

We work for an ISP and pretty many of the customers bought this Exchange server stuff from a third party (we dont sell MS / NT mail solutions).

Often, they run a MS Ex or Notes next to our linux isdn server, which transfers incoming mail to their neighbour.

We get many calls from those who shipped the NT,

  1. we see immediately what's happening
  2. we have full remote control over ours
  3. their NT is mostly the cause

actually, a sad thing.

A reply for the Exchange advocates (0)

Anonymous Coward | more than 15 years ago | (#1775847)

If Exchange is so great for serving a large number of email clients, why did Microsoft themselves refuse to use it for MSN?

Brief historical note: the original plan was to use Exchange for MSN, but after a quick evaluation, the MSN engineers decided that Exchange would require a server for each 100 users or so, so they wrote their own email server within a couple months (probably based on open source) and use that instead.

Conclusion: Exchange is such a piece of crap that even Microsoft refuses to use it, and you want us to base our system on it?

There is also tons of ancedotal evidence of people having trouble with exchange, and basically it requires a full-time admin just to keep it running.

Re:Make It Database-Driven (0)

Anonymous Coward | more than 15 years ago | (#1775848)

You want to make sure that your server can efficiently retrieve data from large individual mailspools if you're going to be dealing with large attachments. More traditional mail servers do a pretty poor job of handling mailboxes > 10Mb. You may want to look at modifying an existing MTA to utilize a database or purchasing one that is database-driven to best suit your needs. Hope this helps!

The maildir format should solve the problems of large mailspools. qmail supports it natively, there are procmail patches for it (perhaps by now it ships with support for it) if you're willing to use procmail as your local delivery agent. There are pop servers that support it natively, and patches for others.
25,000 isn't a huge number of users. I would expect a high-end Intel box running Linux (or *BSD) to handle it with no problems. The main concern, based on my experience on somewhat smaller mail servers, will be disk speed. Lots of RAM will help somewhat, but a RAID would probably also be a good idea.
If they were willing to pay for the software and hardware required for a MS solution, however, you may want to spend it all (depending on the politics of the particular company). Personally, I'd investigate a Sun Enterprise 250, 450, or 3000, and any external hardware RAID. Nice hardware.

Sendmail, and BSD (0)

Anonymous Coward | more than 15 years ago | (#1775849)

I did something very similar using Sendmail on a FreeBSD box. I used the Cubic Circle Pop3 daemon during the beging phases of the operation then changed to Popper due to a pushy client. I had no problems what so ever.

Speaking also from an administrative point of view, avoid GUIs at all costs. At my previous postion we used PostOffice 3.5 for NT, and the GUI was unusable whenever we got 300 users in a catagory. We also had HORRIBLE problems with file creation. It would split one email into 3 or 4 files and before we knew it our server would be hanging since we had 20000 files in a directory.

Exchange... not (0)

Anonymous Coward | more than 15 years ago | (#1775850)

I used to work at a company where we used Exchange for about 5000-8000 people. Everyone had TONS of attachments. The typical user's mailbox was 20+ meg.

The system worked. But the sys-admins had to reboot the servers every week or so. They would lock up otherwise. The worse part about rebooting was all that disk space made the reboot take HOURS... The servers would occasionally lock up for no reason even with the rebooting.

They also needed about 25 dual processor Compaq servers (and they were adding more every month or so) to handle all of this.

But we could use the MS/Outlook/Exchange scheduling and stuff, which is nice. If you don't need that, I'd go UNIX if at all possible.

Re:What about Hotmail ? (0)

Anonymous Coward | more than 15 years ago | (#1775851)

shure? Another reason why Slashdot needs to
spell-check all of the incoming comments.

Anyways, Hotmail runs a patched version of qmail.
Another one that has come up recently in
discussions on debian-devel is postfix
( Check it out.

Is 25k users an absolute max? Then FreeBSD = OK (0)

Anonymous Coward | more than 15 years ago | (#1775852)

A large ISP I know of :-) once used FreeBSD to support ~ 25K users' email accounts, that was pushing it's capacity, on pentium pro 180MHz box, but it did handle the load quite admirably but slightly more than 25k started to sink the ship so to speak. However the rate of new accounts being added pretty much made having only 32-bit UIDs a very soon forseeable serious problem. If 25K users is you absolute max, then FreeBSD will do great for least money spent. Just be sure to use wide ultra scsi disk and most RAM and fastest CPU you can afford. Single CPU is ample, SMP is wasted money for such machine. If you forsee many 10's of K more users in future growth, you need to get a unix that support 64-bit UIDs in filesystem, like Compaq True64 (DEC Unix .... an Alpha box will do the job quite very nicely.), Solaris 7 on UltraSPARC box, or similar competing product.


Netscape Messaging Server 3.6 (0)

Anonymous Coward | more than 15 years ago | (#1775853)

Netscape Messaging Server is wonderful...unless you're using version 4.0x (Solaris)

There are known memory leaks in 4.03...smtpd will drop unexpectedly, admin will fill up /tmp taking down your ability to use telnetd to fix it...a nightmare...but 3.6 doesn't seem to exhibit these problems...

However, supposedly Netscape is working on these problems diligently, and they should be solved by the end of this month! So either wait a little while, or put 3.6 in there won't be dissapointed

If Netscape people are reading this (We all know you are), let's get those fixes out ASAP!!!!!!!!!

Re:25000 users on NT? good luck. (0)

Anonymous Coward | more than 15 years ago | (#1775854)

i agree, one of the companies I work at has a SBS with 23 users, its a nightmare. Not to mention trying to back it up.... I have had nothing but problems with the ArcservIT Exchange Agent.... what does tech support at CAI say "oh yeah we broke that, ya gotta do this....


But I guess thats incuded in the "Lower Operating Cost".

Exchage vs open source (0)

Anonymous Coward | more than 15 years ago | (#1775855)

Exchange has many features, but it is not the most reliable system around. I would rather use another system such as qmail. It may not have all of the bells and whistle that exchange has but it's a lot more stable than exchange. I don't know who in your organization is pushing for exchange, but they're probably non technical people. Good luck trying to get 25,000 user on exchange

Q-Popper (1)

Anonymous Coward | more than 15 years ago | (#1775984)

Hmm, Why not use a linux box (just use some good hardware, like UW2-SCSI to start with), and use Q-popper, its used by many ISP's.. works OK for me

What about Hotmail ? (1)

Anonymous Coward | more than 15 years ago | (#1775985)

Although they ahve not released the source they are mostly opensouce based. I am shure, given enough horsepower a Linux / FreeBSD solution with perl or php (or C if you are brave) could handle this.

Will 25,000 user licenses for Exchange not cost the euquivalent of the debt of a small African country - Why not send it on developers to make a (or another as IMP or TWIG may scale that big) free solution in C, Perl or PHP.


Re:FreeBSD (1)

Anonymous Coward | more than 15 years ago | (#1775986)

How in the fuck does this piece of repetition get a 3 point rating? It says nothing.

Blitzmail (1)

Anonymous Coward | more than 15 years ago | (#1775987)

This will seem somewhat unorthodox, but I would highly recommend taking a look at BlitzMail from Dartmouth College. This solution uses an IMAP-like protocol (but supports POP too) and was originally designed for Mac clients, but its track-record alone makes worth taking a look at.

Consider this:
* Very, very efficient. A cluster of six NeXT boxes used to serve 15,000 accounts, and handled more than 200,000 e-mails a day. AFAIK, these machines have now been replaced with 6 Alphas.
* Unbeatable durability. It was first developed in 1987, and has been in continuous used for more than 10 years! Being a non-commercial product it has not suffered from featuritis or bloat. In other words, it has a very solid code-base.
* Excellent scaleability. It is designed so that you can simply slot in another machine in the cluster to improve performance.
* A great feature-set, in particular it has an excellent real-name based user-database as its core, with secure random number authentication.

And yes, it is free. Source code available etc.

Take a look at:

Skip through the client bits and you will find links to the server software.

Not Netscape... (2)

Anonymous Coward | more than 15 years ago | (#1775994)

I'm familiar with one setup that used Netscape's messaging systems and they can become a total nightmare. There are lots of wierd quirks about the way it handles aliases, etc, that can be a real giant pain.

I've never tried any of the open source products on any large scale so I don't know how they perform. I wouldn't go with Exchange if you are looking to do good scalability. It would be nice to run the service on a big beefy box, and Sun boxes are far better than Intels.

Re:25000 on NT? (1)

Zack (44) | more than 15 years ago | (#1775995)

Unqualified response.

I saw an NT box running exchange for only about 20 people and the damn thing would keep crashing once a month or so. We moved to Linux / Sendmail / CuciPOP and everything was all good.

I'm sure FreeBSD would work as well...

Exchange Experiences with 2000 users (1)

dbarron (286) | more than 15 years ago | (#1776001)

While I am not (thank god) the Exchange Admin, over the 2-3 years we've had it, we've had 2-3 complete mailbox corruption issues and lost the entire database. We've had 3 weeks or so total where it was unavailable (3 1-week blocks).
It doesn't scale well at all (NT doesn' Exchange doesn't) and those boxes look in pain as they try to do what people ask them to. However, response-wise, it frequently "pauses" to check new mail and your composing is also paused...what a great product! :) I am frequently asked by management, why it's so slow.
Unix solutions will be far less headache if anyone understands Unix in your environment and the support is gonna be worth training someone, versus paying Microsoft to vainly (in our case) strive to repair your dead Exchange databases/servers. Our company is STILL headed into a MS only environment and it's sickening. Ok...enough rant and rave.

Qmail is a good way to go (1)

Erbo (384) | more than 15 years ago | (#1776002)

When I recently had to design a Web-based email service as part of my company's "portal" site, I chose Qmail as the "back end" of the service. I set it up to use a virtual password service (I took one called "vchkpw" and modified it) and set up hashed mail directories to keep the directory structure balanced. I also created a miniature HTTP/CGI server in Perl (it didn't have to be fancy, and it uses the UCSPI-TCP "tcpserver" program for its network front end) and employed some Perl scripts and C programs to allow mailboxes to be created and deleted via an HTTP operation. On our public site, this runs under Solaris; for development purposes, I used Linux.

On the Web server side, sadly, it's Windows NT and IIS/ASP, with some ASP components including a custom-written client-side mail store. We use the commercial AspHTTP component from ServerObjects to send requests to the mini CGI server on the Unix box when we need to create accounts. We also use AspMail and AspPOP3 to handle sending and receiving messages. (The mail server is firewalled, so you can't connect to it from the outside with POP3.)

Qmail is definitely industrial strength and free, two qualities that we appreciated. It's also easy to configure and fairly easy to customize. Recommended. Oh, and you can find the end result at [] .


FreeBSD (0)

drwiii (434) | more than 15 years ago | (#1776003)

This sounds like an excellent project for FreeBSD to tackle. I've deployed large mail stores and mail servers on FreeBSD and BSD in general with no problems.

IMAP's Problems (1)

Jordy (440) | more than 15 years ago | (#1776005)

I've recently investigated into switching users from POP to IMAP and have realized that IMAP simply doesn't scale well. Client CPU for doing the type of operations IMAP does is cheap, while server CPU is expensive.

Cyrus and UW IMAP are not light solutions. They are very large binaries which run from inetd and are anything but clean implementations.

Really, I'd say stick to POP3 using something like Qpopper or go with a commercial vendor. Qpopper is probably the best POP3 server you are going to find in the OSS world, though it does still run from inetd.

Open source POP3/IMAP4 servers really are lacking in the Unix world once you get past a certain number of users.


Exchange 5.5SP1 fixes this (1)

soellman (993) | more than 15 years ago | (#1776025)

I believe.. But that's still no excuse for the substandard spam-handling of Exchange versions prior to 5.5SP1, you could control which IPs clients can connect from (tcp-wrappers, basically), but that's a layer 3 solution (and a bad one, at that) to a layer 4 problem.

an MCSE who hasn't used MS products in 15+ months..

You're looking for Cyrus (1)

dgreer (1206) | more than 15 years ago | (#1776028)

Check out index.html [] for info.

As for the MTA, well I've seen plenty of votes for Qmail and Exim. I'm still pretty partial to Sendmail though. I think they'll all work (though I've been told Sendmail on a single server probably would have a tough time keeping up with the load on something like this).

With all of these solutions, if the users are getting much mail, you'll probably have to do something kind of exotic to break up the mail requests across multiple servers. The more transparent you can make this, the better. Either the users will have to know WHICH server thier mail goes on, or you will have to make the multiple servers ALL have access to ALL the mail.

One possible solution would be to use something like CODA (also from CMU [] ). This is a cacheing network file system that you could set up on a backend server (running over something like a multi-ported 100Mbps Ethernet Switch with the multiple client servers on the front-end exposed to the network). When client server "x" gets a request from "joe", "x" accesses the file system and gets all the files in joe's mail box (a series of directories) (the ones requested first, then pre-caching all the others). When joe stops using his files, they are allowed to expire on "x" (releasing the cache for use by mary, or adam). Once downloaded, the files can be manipulated on the client and changes are sent to the server when there is time/bandwidth (I'm not sure how the locking and similar mechanisms work on this ... read the coda docs for details).

This way, you can dedicate one or more MTA servers to stuffing mail into the backend CODA server, then have one or more client servers pulling the data out and handing it to the clients. You spend most of your money getting a BSB (Big Stinking Box) for the backend, and use cheap, easily-replacable-if-it-crashes machines for the front end.

Another nice thing about Cyrus: It allows you to set per-user space limitations and access restrictions, and mail sent to multiple users is put into a special cache directory meaning it doesn't take up space for each copy.

One warning: Cyrus suffers from the same problem as INN's traditional storage system - it eats the hell out of inodes because each message is a file. Most email messages are in the 1-2 K range, so when you create the filesystem for Cyrus, make sure to create the maximum Inodes.

I know from the docs that CMU uses this on a 10000+ user mail network, and they apparently are quite happy withit. I've heard similar things from other large sites.

Basically, Cyrus is what Exchange hoped to be :^).


Re:No recommendation... (1)

X (1235) | more than 15 years ago | (#1776029)

Just in case anyone didn't know this, the Cyrus IMAPd fully supports public folders. Scheduling is another matter. For that you need an open source calendaring project. ;-)

Cyrus probably a good bet. (3)

X (1235) | more than 15 years ago | (#1776030)

The Cyrus server at CMU is probably your best bet. You'll find it at at this link [] .

It's worth noting that this project is currently supporting all of CMU's e-mail needs. It's also my understanding that it forms the basis for Netscape's Message Server and Post.Office. This should satisfy any concerns about it's scalability. It has lots of handy features like kerberos authentication, a database style message repository, support for ACAP, etc.

Alternatively try QMail [] . Personally, while I think it provides better SMTP performance than Sendmail, I'd rather use the Cyrus IMAP server than the UW one (the only one supported by QMail). You could go with using a combo of sendmail|postfix + Cyrus for incomming mail (i.e. what your MX records point to) and QMail for outgoing mail. It depends on your performance needs

Exchange Server is NOTORIOUS for being both difficult and expensive when you need it to scale to a large number of users, although I understand it's improved substancially since the 4.x days when it was just impossible.

The disk subsystem is the bottleneck, kids! (1)

nickm (1468) | more than 15 years ago | (#1776033)

Sorry man, throwing more CPUs at the problem of mail is not the solution. What you need to do is get a very fast SCSI/raid controller and some high-RPM low-latency/seek time LVD drives or something. Large CPU won't help, since mail is mostly a matter of throwing files from disk to disk over the network. I mean, this isn't heavy rendering or anything.

So get a good, fast disk subsystem and attach it to whatever Unixoid OS you like. Run Qmail if you like (it's a bitch to configure, and not as versatile as sendmail, and it's not open source but it's fast), or get a bunch of good sendmail admins.

You can configure any mailer to handle large load on the SMTP side of things by using multiple MX records and mail relays. POP and IMAP are a little tougher.
I noticed

Cyrus and Exim (2)

RobKow (1787) | more than 15 years ago | (#1776037)

I've had good luck using the Cyrus IMAP server and the Exim mail transfer agent (MTA). The Cyrus server handles POP3 and IMAP, and stores the mail in an internal file per message format, and is designed for hosting mailboxes for those without accounts on the system. I've found both Exim and Cyrus to be fast, secure, scalable, and stable for thousands of customers, and I don't see any trouble scaling it further.

Re:Exchange => Pain (1)

Harry (2006) | more than 15 years ago | (#1776040)

Ya, cyrus works wonderfully @ if someone would only get sieve working .


I worked for a 25k user ISP and a 1.2mil one now (1)

kashani (2011) | more than 15 years ago | (#1776041)

Setup at the old ISP was this

3 ultra 2's
512MB RAM each
30GB array by artecon that was NFS mounted.

This was slightly overkill for us. A few this to keep in mind.

1. Have more then on machine running this. I would say use 4 PII's. Use dns round robin for load balancing. If you have the money get a real load balancer. With an NFS disk array and sendmail file locking this isn't hard to administer.

2. Use as much RAM as you can afford. 512MB min. 1GB to 2GB is better.

3. Fast local disks. QPop servers files locally. Have at least 4 gig for mail to be queued. We had at least one user trying to cycle 2 gig attachments through our machines every month, Bastards.

4. Set up qpop (or whatever) in server mode. This will decrease the traffic from you to your raid array. Server mode tels it that it is transfering data across the network, if nothing in the data changes just revert and don't move the extrea traffic.

5. Disk. We were fine with 30, but upgraded to 50GB with the last upgrade. Artecon NFS mounted to the 3 machines. Look at Netapps though. You can cluster them in a failover config. I have heard of some hardware problems with them though. We pushed 16MB/sec across a peak so make sure you are AT LEAST ultra wide if not ultra2. You could set up a server with the disk attached and let it do your NFS instead of a full network disk thingy.

6. I'd suggest sendmail, but qmail is nice, too. Sendmail seems easier to set up to use with pine if you want to hook a shell machine up to it with Pine or use a webmail package, but honestly I haven't played with Qmail much.


Re:Cyrus probably a good bet. (1)

bgdarnel (2144) | more than 15 years ago | (#1776047)

I agree. Cyrus is also used by NCSU, with over 27k students. At there are some notes about how this was implemented.

Re:Hotmail (2)

kdoherty (2232) | more than 15 years ago | (#1776048)

qmail is actually not Open Source.

From []
"If you want to distribute modified versions of
qmail (including ports, no matter how minor the
changes are) you'll have to get my approval."

Please reply in email if you feel the need, I'd
rather not start a flamewar here :)
Kevin Doherty

Re:Hotmail (2)

Whisper (2382) | more than 15 years ago | (#1776049)

Acourding to Microsoft, Hotmail _is_ run on top of Solaris. Check out tmail.asp

They also state that along with Solaris being used, Windows NT is also used, but they fail to mention how/where it is used, so my guess would be as devel, and not production.

My favorite quote from the article is "Solaris is Hotmail's legacy production operating system". bwuahahaha.

Avoid M$ SexChange. (0)

smithdog (3152) | more than 15 years ago | (#1776060)

M$ SexChange is definitely _not_ the way to go. Other M$ products to avoid. M$ Expel. (popular spread sheet) M$ Abcess. (weak data base) M$ Turd. (popular turd processor)

Notes from Linux '99 (3)

linuxci (3530) | more than 15 years ago | (#1776062)

At the UKUUG Linux '99 [] conference there was a presentation explaining how they implemented a large scalable mail server using open source software. It was also explained how the total cost of ownership would be much higher if they used an NT solution (even using the figures supplied by MS they'd need more machines and more administrators to keep the servers runnig).

The open source solution was much more cost effective and has proved fairly stable.

Unfortunately the proceedings from the event are not yet online, however I'll try and forward you a copy (or post a link to this thread) as it may prove useful to you.

Make It Database-Driven (1)

dew (3680) | more than 15 years ago | (#1776064)

You want to make sure that your server can efficiently retrieve data from large individual mailspools if you're going to be dealing with large attachments. More traditional mail servers do a pretty poor job of handling mailboxes > 10Mb. You may want to look at modifying an existing MTA to utilize a database or purchasing one that is database-driven to best suit your needs. Hope this helps!
David E. Weekly (dew, Think)

University of Washington (1)

michael (4716) | more than 15 years ago | (#1776071)

Well, for us (University of Innsbruck, Austria), the UWash IMAP server works well. We do serve nearly 20.000 users using a SGI Challange dm workstation (a powerful Intel or Alpha dual processor would do the same job I suppose - those SGI machine is 4+ years old ...). There are no problems so far (8 month).
However, we did some minor modifications - we do use dmail from imap-utils for mail delivery (does integrate well with procmail, too), changed to MBX style mailbox formats and changed the default mailbox lookup from ~/mail to ~/. Everything else is quite standard. We do not have any problems at all. The users do access their mail using Netscape Messenger (IMAP), Outlook Express (IMAP), pine (local or IMAP) or IMP.
The only problem is that there are many processes (especially due to mail checkers). Normallly, this isn't a problem. But we do also offer a modified version of IMP for our users to access their mail worldwide. IMP is very slow if the server has many processes as it happens to create a process for every single mail when it reads a mailbox. We did modify IMP to overcome the major flaws, but everything else is pretty stand (or at least there are some publically available patches).

Intermail (1)

eGabriel (5707) | more than 15 years ago | (#1776081)

Intermail from Software.Com has POP3, IMAP, and
is designed for the 5000+ client market.

It is pretty easy to configure, and if it is like
their other product, Post.Office, a Unix version is available.

I guess I have never run a system with that many users, but wouldn't an appropriately beefy
set of boxen with a clever DNS MX scheme, running
Sendmail, and the freely available POP3 and IMAP4 daemons of your choice do the trick?

Re:Exchange => Pain (1)

ts4z (5791) | more than 15 years ago | (#1776082)

Er, that link didn't quite work, wtf?

Anyway, that should be Cyrus [] , or more specifically, the Cyrus imapd [] .

Exchange => Pain (3)

ts4z (5791) | more than 15 years ago | (#1776083)

I've never heard about anyone really happy with Exchange. Except maybe Microsoft, but I'm pretty sure they drug the water.

Check out Cyrus, from Carnegie Mellon, which is gratis (but not free).

Or maybe you'd like to spend some money. Then there are lots of companies, like Mirapoint [] , who I work for.

Re:I had Exchange to work well (2)

CMiYC (6473) | more than 15 years ago | (#1776089)

That's amazing... we've got 18,000 users using qpopper on a P2-233 ... and no sweat.

Amazing how little hardware we had to use.


Re:Exchange bad, any UNIX Good (1)

Milosch (8290) | more than 15 years ago | (#1776097)

Not to mention the bug/hotfix routine and a
proprietary database scheme which is tough to

One bug I ran into recently dealt with the
Internet Mail Connector. If you set global
limits on the size of user mailboxes, IMC
will bomb when it hits that limit - Keep in
mind it handles internet mail for all users
on that server. Yes, there is a fix. I
have not tried it yet, as I have to go through
the phone call screen at MS first.

don't forget a good LDAP sever program... (1)

Barbarian (9467) | more than 15 years ago | (#1776103)

Especially if it's in a corporate environment. And do NOT try to get 25000 email users on one box with MSEXCH.

Exchange limited to 16GB? (1)

Unit3 (10444) | more than 15 years ago | (#1776111)

AFAIK isn't Exchange limited to a total of 16gb of mail messages? Isn't that only like 670k/mailbox for 25000 users? =)

Large Scale free email (5)

Outland Traveller (12138) | more than 15 years ago | (#1776116)

When you have that many users you have to have a nice structure for the usernames, which isn't the /etc/passwd file. And, you need a mailbox format that isn't linear, like the normal mbox. The rest of the problems can usually be solved with hardware (think about using a raid).

I know of three potential semi-free solutions.

Carnegie Mellon Cyrus (go to the FTP site and download the latest version. Don't rely on the way out of date web page to link to it.) IMAP server.

University of Washington's imapd. This seems to be under more active development, and supports a nice range of features, mailbox formats, and security mechanisms. However, it uses the passwd file (although you might be able to get around this using PAM) and it doesn't natively support quotas. (although you can do this at the OS level.

Darthmouth's Blitzmail Server: This has been ported to linux, and is *wonderfully* scalable across multiple machines. It inlcudes its own directory services too. The only problem is that it doesn't support Imap (although some work has started on that front), and the only database it supports as a backend is oracle. I would love it if someone hacked it to use mysql of postgresql with IMAP support, but that's a tall order. The client is also under-featured.

All of these have their drawbacks though. You might wish to go with a commercial IMAP/POP server on linux. There are a few good ones that exist. You definitely don't want to go with exchange. A lot of people go that route because they are forced to. My experience with exchange 5.5 was so bad that I would not recommend it to anyone.


Re:Hotmail (1)

Azul (12241) | more than 15 years ago | (#1776117)

Umm. I understand they do use Solaris on their SMTP servers. I did a nslookup for their MXs and then tried to use Queso and telnet to different ports but couldn't find a way to prove that has Solaris.


Manual user creation (1)

DHartung (13689) | more than 15 years ago | (#1776128)

There are wizards and things, and there are ways to have Exchange create mail users automagically from an NT Server userID database, but it definitely is a pain. I believe there are third-party products which do simplify the process.

Hotmail (2)

Jethro (14165) | more than 15 years ago | (#1776130)

I believe Hotmail use Qmail, which is open-source. When MS bought them out they tried to switch to NT/Exchange, but couldn't get it to work, so they're back on Solaris/Qmail now. I believe they support a large userbase which not only have attachements, but a whole lotta spam, to...

Re:NT (1)

Null_Packet (15946) | more than 15 years ago | (#1776138)

I think this is a cop-out. Exchange has proven itself to be quite stable, and is one hell of a solution for many, many people. Exchange will handle 25k users, the only limitation is the restore time to restore IMAP data stored on the server. If you use POP3, that problem goes away as the files are retrieved from the server and saved on the user's local machine.

What you should consider is using sendmail for smtp services, with and Exchange frontend. This lets you do all the cool stuff, but keeps it running nice and fast. Email me at if you want more info.


Re:25000 users on NT? good luck. (1)

Null_Packet (15946) | more than 15 years ago | (#1776139)

Fire your Exchange Admin... wait! Is he the janitor, the LAN admin, and the mailroom clerk too? Try not to be so quick until you have seen some big sites use it.

How much would 25000 users cost? (1)

SoftwareJanitor (15983) | more than 15 years ago | (#1776141)

What would just the client licenses for Exchange cost for 25000 users?

How much would all of the copies of NT Server and Exchange you'd need (you aren't going to run that many people on one box, that is for sure) to support that many users with Exchange cost?

How much is all of the technical support you'll need from Microsoft going to cost?

How many MSCE's will you need to hire to administer all of those NT Servers?

Etc, etc.

My guess is you are talking costs in excess of a million dollars more to implement NT/Exchange than it would cost to implement an open sourced solution.

Re:Q-Popper (1)

Bombcar (16057) | more than 15 years ago | (#1776142)

You can use a linux server to server HUGE numbers of users. I set one up for a telecommunications server. It has only one problem - you have to rotate the logs from sendmail or the system will BOG DOWN HARD. This happens when the logs get to be about 10 megs each. Just need a Pentium Pro at 200 MHz or maybe dual and gigs of space and gig of ram (That's what the system was)

Exchange bad, any UNIX Good (1)

Mazzella! (16436) | more than 15 years ago | (#1776144)

Exchange is just a plain pain. The senate uses it for, what, maybe 1000 users (Senators and support)... When they were flooded with email last year, the servers locked up totaly. Many messages for days on end were lost. A cluster of Linux boxen would be a bit overkill, but if you wanted to do it, it would be a far better solution than ANYTHING Micro$oft.
If you need some white papers to convince your boss(es) go to: []

Why not InterMail from (1)

Gumber (17306) | more than 15 years ago | (#1776147)

I have no doubt that you could eventually build a reliable system from open source tools, but you should give serious consideration to a carrier class software like the stuff from I beleive their licensing starts in the 25,000 mailbox range and goes up, which should be a hint that they are ready to meet your needs.

Consider this 25,000 mailboxes * 10 MB/mailbox =250 GB. Is this something you are ready to trust to your linux filesystem without a second thought.

If you are going to roll your own you should dig around on They have a document which describes how earthlink built thier own e-mail system on top of a net-app filer.

Re:Outlook doesn't scale, duh, it is a mail client (1)

Gumber (17306) | more than 15 years ago | (#1776148)

Of course outlook doesn't scale, it is an e-mail client, not an e-mail server.

Perhaps you meant exchange server. If you did, I would have to agree with you. Exchange server would be wrong for this sort of arangement.

25000 users on NT? good luck. (1)

chewie124 (18786) | more than 15 years ago | (#1776152)

My company has enough trouble trying to have it work with under 50 users.

25,000+ on exchange (1)

iceaxe (18903) | more than 15 years ago | (#1776153)

My current employer has more than 25,000 users on Exchange. It works fine except that exchange crashes every other day! ;-)

My last employer had a similiar load on exchange servers, and it seemed more reliable there. Then again, my last employer had access to more knowledge about exchange and NT than any other company there is. ( Guess who? [] )

I'd concur with the other posts that suggested something on a proper enterprise scalable real OS.


Don't use exchange - scalability and $$$ reasons (1)

jaykamm (20958) | more than 15 years ago | (#1776159)

Exchange is absolutely unusable in your situation unless you have unlimited financial resources for 5 times as many machines, corresponding sysadmins, and here's the kicker: licenses.
You'd have to license both NT Server and Exchange server for 25,000 users [the nt server is a little different, but exchange def. the 25k ].
It was prohibitively expensive for a 50 person insurance office, so it would kill your operation. I setup a linux box for them a year ago, and haven't touched it but three times since, all b/c of extended power outages...

Sendmail on Solaris (1)

austad (22163) | more than 15 years ago | (#1776163)

The University of MN hosts over 75,000 email accounts using sendmail running on Solaris. I'm not sure how big the Solaris box is though, but buying yourself $100,000 worth of Sun equipment and using sendmail is still going to be *WAY* cheaper than going with Exchange.

Qmail is fast and easy to set up, but lacks many options that are available with Sendmail. Sendmail also has built in support for the Realtime Blackhole to filter out spam. Sendmail is definitely the way to go. As for the machine you run it on, you can always get some Sun Ultra 2's, and cluster them together. Maybe an A5000 fibre channel file library too.

You could try running it on a 4 processor Xeon running Linux, but I don't know if x86 processors could handle the load. I seriously doubt it, especially in the morning when everyone is checking their mail. Go with a RAID setup to speed up disk access. And you may want to turn off logging for the mail, syslogd take up an awful lot of CPU when we turn on logging for mail. If I was on a very restricted budget, I would try Linux on a 4 processor box from VA Research with sendmail compiled with pentium optimizations, a really big RAID array, an optimized kernel, and lots of memory and no mail logging. Of course, I'd be ready to plug the old mail system back in very quickly just in case.

Re:Exchange => Pain (1)

the_ed (22189) | more than 15 years ago | (#1776164)

Yeah, I'll second that. I've had an Exchange server spontaenously spawn 3 seperate problems in 2 days, not to mention it gobbling all the space on the HD. The boss was also quite put out when Exchange couldnt handle a 500k attachment he was sending, which promptly went through when it was sent through QMail on a FreeBSD box.

Just my little rant. But Exchange does suck.


Well, over here at Cisco... (5)

kend (22868) | more than 15 years ago | (#1776166)

Sendmail's the answer for us. The only thing that hasn't scaled well is plaintext aliases files: we've got some 20K mail lists, and it's beginning to get somewhat messy, so we're having to go to the non-plaintext solution. But for all the rest, it's stock sendmail with various GUI backends for end-user ease-of-use (and security). Note that we don't have 25K users, but 17K isn't that far off, and we do a *lot* of e-mail.

Re:Exchange limited to 16GB? (1)

Madduck (23916) | more than 15 years ago | (#1776169)

That was v5.0 v5.5 has unlimited (well really limited by available disk space) storage

No recommendation... (3)

FascDot Killed My Pr (24021) | more than 15 years ago | (#1776172)

...except an anti-recommendation.

If you are going to setup 25,000 users, do not, repeat NOT, use Exchange. I remember our migration of a mere 750 with extreme horror. We had to manually create each user.

Of course I was simply a lowly programmer working under the direction of our totally incompetent network admin--maybe there was an easier way and she missed that topic in the training the week before.

What you really need is a requirements analysis. Exchange is a totally different thing than, say, Sendmail. Analyzing what you need will tell you which to go with. For instance, do you need public folders, scheduling, etc? If so, maybe use Exchange. Do you need configurability, speed and Internet email? Then you want not-Exchange.
Put Hemos through English 101!

Re:25000 users on NT? good luck. (1)

Seth Cohn (24111) | more than 15 years ago | (#1776173)


I am at the end of pulling an NT exchange system because it never worked right ONCE. I had users who couldn't access it reliably at all. I figure 20% failure on a regulaur basis. Email that was misdirected often (forced to use MSmail, not internet STMP address, which is what we wanted)
The nightmare is finally over... and this was only 50 users.

(Back to the linux system, which has never failed once... huge uptimes, 100 users....)

Netscape Messaging Server (1)

Mr. Spock (25061) | more than 15 years ago | (#1776176)

We use the netscape messaging server here. This was a compromise between the exchange solution that some people wanted, with all of the coporate wightbehind it, and the sendmail/unix open source solution that other might prefer. So far we've had pretty good success with netscape messaging server using Netscape's enterprise LDAP server as a directory on the backend. There's a pretty gui to show the boss and a great Perl interface for LDAP for myself.

On our unix shell server users can connect to the messaging server via IMAP, and they can look each other up in the database as well from within pine. Obviously there's a nice interface to Netscape Communicator as well.

We also have a microsoft exchange mail server here. It's using a number of multiprocessor 300mhz PentiumII boxes, it cost us a fortune, and in my humble opinion doesn't provide the level of service we get from our messaging server.

If a simple sendmail/unix setup won't work for your managers or your environment, you might want to give this a try.

Sendmail @ Netcom (3)

Bryant (25344) | more than 15 years ago | (#1776179)

Upwards of 30K shell users, four Sparc 2s, SunOS 4.x, sendmail. And a lot of email. Our only big issue was the number of files in /var/spool/mail, which we coped with by going to Network Appliance NACs.

We noted that directory lookups got worse in a distinct knee -- i.e., we had no problems for a long time and then we hit a magic number and things went all to hell. I do not know offhand how well linux or Solaris deals with directory lookups, but you could test easily enough.

The thing you didn't tell us was what the volume would be like; the number of users matters for the mail spool but the number of email messages matters for the CPU usage... I suspect that you won't need a very heavy box, though. Email is cheaper than you might think.

Oh. Run a DNS server on the mail hub, to avoid a lot of lengthy DNS queries on some other poor machine. Flush the cache daily.

Lotus Notes? (1)

l4m3 (25501) | more than 15 years ago | (#1776180)

Why not Notes? you will get that kind of scalablity and you can let you boss start you out on WinNT but after they see the light you can switch them to Linux. Domino isn't currently out for Linux, but supposively R5 will be out by the end of the year.

use imap (1)

jauderho (25526) | more than 15 years ago | (#1776181)

Here's a link to get you started []

Have fun and ask if you have questions.

Use HotPOP (1)

Eric Savage (28245) | more than 15 years ago | (#1776187)

HotPOP is a Linux based solution that handles this kind of traffic easily and cleanly. Its probably the most cost effective solution too. Send me an email if you want more details.

Another recommendation for Cyrus (1)

prevost (28302) | more than 15 years ago | (#1776188)

The Cyrus server from Carnegie Mellon does very very well at delivering POP3 and IMAP4--they designed it to be very very scalable. There's one server currently handling the entire campus right now (12000ish people? More? I forget), including an IMAP gatewayed set of usenet. And it still works quite well.

The machine they're using is big iron (a big Ultrasparc with raid and so on), but I don't expect you can handle this sort of load with anything but.

Also of note is that the Cyrus folks are working on ways to do good load-balancing with IMAP (for example, allowing clients to transparently find the right server for a given mailbox).

I doubt very much that any MS solution could scale this well without a lot of effort. Cyrus or some similar piece of IMAP4 software is probably what you should be aiming at.

Finally, if you're only planning on doing mail, and not shared mailboxes or usenet-via-imap sorts of things, and if you have the space not to need to migrate users from one server to another to balance, you should be able to do decent by-hand load balancing right now. (i.e. "your server is")

Re:Another recommendation for Cyrus (1)

prevost (28302) | more than 15 years ago | (#1776189)

visigoth@unix9 ~$ hostname
visigoth@unix9 ~$ wc -l /etc/passwd
19517 /etc/passwd

Some of the accounts are probably defunct, but since the university prunes accounts pretty proactively, I expect the majority are active.

The majority of the above users get mail on the one big-iron Cyrus server I mentioned.

Domino? (1)

nicksand (28560) | more than 15 years ago | (#1776192)

It seems that a lot of the services that people are suggesting are vanilla smtp offerings. If thats all you need, I'd definately stay away from exchange. However, if you need groupware type things (shared calenders, address books, etc), you should take a look at IBM's domino server. Just be aware that you will need a pretty beefy cluster of NT machines to support it; but then again, you'd need just as many machines if you went with exchange. Domino running on top of NT4 with nothing else sucks up about 80mb-140mb of ram (thats with about 40 or 50 user accounts in the system). Mail files get rather bulky (they start off at about 3mb when empty). A port of domino to linux is apparently in the works but is not quite there yet.

Let me warn you though, Domino has its own little quirks you get to deal with, and it has several unintuitive aspects about it. On the other hand, there are also some shiney things about it (eg: webpage access to all services, complete integration of all common communication needs, and extensibility through notes designer).

About Exchange.... (1)

Bob-K (29692) | more than 15 years ago | (#1776199)

One thing you oughta point out to the Exchange advocates is that MS wants to sell you a client license for each computer connects to it, even in an Internet setting. In 20-packs, they're about $55 each, so that would be over $1 million for 25K users. Obviously, a volume license would help, but still.... The money saved by using something else could pay for a lot of custom development.

Be Very carefull... (1)

musicmaker (30469) | more than 15 years ago | (#1776203)

My company has just over 100 employees, and our admin is begging to change to UNIX and sendmail. He hates sendmail configuration, but is so sick and tired of messing with exchange and our antivirus stuff every day that he wants to change _bad_.

The config of sendmail may appear rather odd and difficult, but once you get used to it, it's not too bad. Compared to the vast list of problems in Exchange. We got hit by a spammer using our Exchange server to relay through and 'pretend' to come from our domain to send out to just over 1mil users. The mail we got back choked our mail system. I don't know much about the workings of exchange, but our admin found no way to stop exchange from relaying mail that wasnt for our domain. This is a one liner in sendmail. Sendmail is _much_ safer.

(P.S. For sendmail mail read sendmail/qmail - many prefer qmails ease of config)

Musicmaker :)

TurboCluster from TurboLinux (1)

Raleel (30913) | more than 15 years ago | (#1776208)

You might give this a try. Basically they have a load balancing daemon running to make sure that nothing gets overwhelmed.

At work here we are running about 16 MSexchange servers for about 3500 people. That's about 200/server. Icky....

Re:No recommendation... (3)

ibbieta (31756) | more than 15 years ago | (#1776211)

Yes, please, for your sanity, do not use Exchange unless you have to. It is large and cumbersome and requires a large server with expansive drives for even one hundred users.

I use and maintain an Exchange server (well, three) and the main server consumes 10 gigs of a harddrive and all of a 333 MHz Pentium. This is for about 200 users and most are not that active.

Besides the hardware overhead there are other negatives to Exchange. Namely, it does not route internet traffic well, it has poor error reporting, and it "clusters" badly. I'll take each point one by one.

My company has affiliates in small offices around the world and they have neither the on-site resources or talent to maintain an e-mail server so these offices use our Exchange server as POP3 and SMTP. This creates an open relay and all attempts to close the relay have met with stiff opposition -- users complaining they now have to use a password, cannot remember what domain they are on, and general users resisting change. At the moment, Exchange has no true "Back Office" solution for this problem and I would have to personally configure all of our affiliate offices if I want to completely secure routing.

The error reporting come down to this -- either you log all of the messages passing through Exchange or none of them. I wanted to log the messages that caused errors for obvious reasons and after about 4 days noticed the drives filling up with archives all all the messages, not just those messages generating errors. Microsoft admits this is a problem but there is still no fix, at least not in SP2.

And finally, "clustering". I'm not talking about true clustering but instead about using multiple Exchange servers to distribute the load somewhat. We have two e-mail domains and wanted to start putting people on the second domain to balance the load. Each server runs fine on its own but for some reason they hate talking to each other. The replication services keep stopping (pausing, really) and site connector is more frustrating than helpful.

I have not had many problems with our Exchange server otherwise. It runs forever and reliably. It has the longest uptime of any of our NT machines, only needing a reboot every month or two. However, I'd think long and hard before accepting a job caring 25,000 user's e-mail if the server were NT. Anything over about 1000 users you should look elsewhere if you can.

Scaling the box might be the real problem... (2)

sam_vilain (33533) | more than 15 years ago | (#1776219)

Handling a 25,000 active user base on one machine might be a problem for intel machines, and (dare I say it), most Open Source OS's.

Solaris will do this, but you will probably need to run it on a _big_ box, like a Sun Ex500 class machine with about 8 or more processors. And get their SIMS product, too, it's pretty well optimised for the high end. Other high end commercial unixes like AIX and IRIX will no doubt scale this far as well.

If you are able to go distributed (ie, the organisation is easily divisible geographically), then something like Linux or FreeBSD with qmail or smail will probably cut it.

Beware that exchange servers offer a fairly high level of integration with Outlook, which a product based on open standards will not be able to deliver.

Re:Not Netscape... (1)

bbarrett (33853) | more than 15 years ago | (#1776220)

We use netscape's mail server for a 2,000 user mail forwarding service. We had some trouble with SPAM filtering, but that was because we were idiots. After we read the ENTIRE web page on setting up the filters, all was cool.

Netscape does have some funny quirks in how you have to set up the accounts. I don't remember all of them, but the "proper" ways to do things are well documented. Also, the Netscape Admin Server is nice and easy to use.

My experiences have been with Netscape on Solaris, but I understand the Linux version is very similar.

Go to (1)

malice95 (40013) | more than 15 years ago | (#1776233)

Go to they have a document
there about building large mail systems that gives
you a lot of the ins and outs. has
a nice gui that makes managing everything easy..
and definatly setup a HA solution with 25k users.
I have a friend in Microsoft's Messaging group,
His response was.. "25k on exchange? Heheheheh"
open source is the way to go with this size
system. I have set up several 5 and 10k user mail
systems and open source has never failed me yet:)
IMHO I would go with a sun product for
reliability. Uptime will be your number 1 concern.


How about qmail? (1)

speckled_trout (41254) | more than 15 years ago | (#1776242)

I have actually rolled out an exchange site of that same scale but for my brother-in-law's small business I setup qmail,, as my first Linux project. Its great and easy to manage, I have rebooted the box maybe once and that wasn't for any problems with qmail. There is a mailing list where you could ask about scalabilty. All Exchange sites of that considerable size do it with a multitude of servers. I think you can make several qmail servers talk to each other. I wish there was something in the open-source community that had all the features of Outlook(except Journal). That's what is really needed to switch the PHB's around. (1)

mattfusf (43660) | more than 15 years ago | (#1776248)

While not an open-source solution, I used InterMail at a previous job. It worked very well on NT - it handled a few thousand POP3 accounts without breaking a sweat. I believe they also have versions for a couple of other systems - check out


Outlook doesn't scale, look at other solutions (4)

anticypher (48312) | more than 15 years ago | (#1776251)

Having to still support an old network installation run by a bunch of idiots (they are attempting to implement a mostly micro~1.oft shop), I can tell you that outlook doesn't scale to more than 2000 users before the maintenance starts to become a headache.

This is a large client trying to implement a server farm of 20+ NT machines, each server supporting 600-800 users, and combining the whole lot into a coherent whole. Fortunately I only have to fix their poor network designs. The team of administrators now numbers more than 50, most are MCSEs, none less than 5 years experience with Micro~1.oft products. They are tearing their hair out on a daily basis. Complaints number in the hundreds every day, and thats just the users who haven't given up completely.

My advice is to start looking at the larger commercial products, possibly Netscape's server. Get a reputable vendor to support it.

If you look at open source systems, start with OpenBSD and NetBSD.

Divide your system up between the MTA doing delivery/reception of the messages, and the MTA serving the users. Its ok if email to the outside world goes down for short periods of time, its almost expected. But if users cant get to their mailbox 100% of the time, you will look bad.

You also need to look at managing more than 32000 or 65000 users in the future, remember that various *nixes have either 15 or 16 bit UID fields. You should make sure user accounts/authentication/logins are separate from any UID system on any machine type. This means getting some kind of medium sized DB, and tying it into your auth and login schemes. Others have done it, its not that hard (look at AOL with 10million+ user accounts)

the AC

A request for rewd (2)

plopez (54068) | more than 15 years ago | (#1776255)

No matter what solution you pick (or gets chosen for you) would you please report back to us with how it went? It would make a great case study either whether or not MS can handle a true enterprise level application or how well FreeBSD/Linux/whatever handles it.


Re:Hotmail (1)

z4ce (67861) | more than 15 years ago | (#1776274)

Perhaps Qmail, but they don't run solaris. I've heard this common misconception, I have to wonder if it was published somewhere go to Netcraft [] and type in hotmail,com

Exchage, only for big bucks. (1)

ZTechNet (69041) | more than 15 years ago | (#1776280)

My friend was hire full time by a large computer company, they have many people in many remote sites. He has now been there two years and still does not have exchange working correctly, even for the one main site of 1000 people. So if you want to spend the rest of your professional career futzing with exchange, or paying someone, then go ahead. Otherwise, UNIX is the way, I see no reason that an open source soltion. Remember split up the load, boxes for sending, boxes to handle pop, and one big ass box to store all of this.

Exchange (1)

bob4u2c (73467) | more than 15 years ago | (#1776292)

If you had about 3,000 users, exchange would work. However, it's not very scalable (contrary to their propiganda). The staff here was forced by the college network to switch over to it so that we could read and use the documents students were sending to us. To it's credit it's pretty flexible, but when the time came to switch the students over to it Microsoft said that it couldn'
t support 20,000+ users. Also from what I've seen of the budget it was a pretty hefty price, even with an educational discount!

Re:Not Netscape... (1)

Brandon Hume (73471) | more than 15 years ago | (#1776293)

> IMAP. Plus, unless you completely customize it,
> sendmail will store mail in one giant file per > user,

Incorrect. Sendmail uses the local delivery
agent in the final delivery process, and this
delivery agent can store the mail however it

An example is the Cyrus IMAPd, which uses its
own delivery agent to store the email in the
newspool-like message tree. Using the delivery
agent is less than a one-line modification to
Brandon Hume
hume -> BOFH.Halifax.NS.Ca, http://WWW.BOFH.Halifax.NS.Ca/

Solutions (1)

atrus (73476) | more than 15 years ago | (#1776294)

There have been many posts on this already, but here is my two cents.

I'm not completley expierienced with making mail servers which are THAT big, but I can guarantee you Exchange will not handle it. You're looking for a FreeBSD machine, dual, maybe quad, processor, RAM galore (> 512), and, of course, the hard drive space to go with it.

For the SMTP agent, look at qmail, or if you're gutty, sendmail. You might look at a third party software package for this.

For the POP3/IMAP4 agent, look into UW-IMAP4. I've had it work with over 100 users on a single dinky Pentium 166 w/32 MB of RAM running FreeBSD.

Large Scale Mail System... (1)

gnu (73486) | more than 15 years ago | (#1776295)

check out

It's how Earthlink does their Mail system with Sendmail, and Qualcomm's POP daemon version 2.2.
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