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Fight Spam With Nolisting

kdawson posted more than 7 years ago | from the noncompliant-spambots dept.

Spam 410

An anonymous reader writes with the technique of Nolisting, which fights spam by specifying a primary MX that is always unavailable. The page is an extensive FAQ and how-to guide that addressed the objections I immediately came up with. From the article: "It has been observed that when a domain has both a primary (high priority, low number) and a secondary (low priority, high number) MX record configured in DNS, overall SMTP connections will decrease when the primary MX is unavailable. This decrease is unexpected because RFC 2821 (Simple Mail Transfer Protocol) specifies that a client MUST try and retry each MX address in order, and SHOULD try at least two addresses. It turns out that nearly all violators of this specification exist for the purpose of sending spam or viruses. Nolisting takes advantage of this behavior by configuring a domain's primary MX record to use an IP address that does not have an active service listening on SMTP port 25. RFC-compliant clients will retry delivery to the secondary MX, which is configured to serve the role normally performed by the primary MX)."

Sorry! There are no comments related to the filter you selected.

Oblig. (5, Insightful)

Whiney Mac Fanboy (963289) | more than 7 years ago | (#17719106)

YASIGFINFE (Yet Another Spam Idea Good For Individuals, Not For Everyone) - Spammers will change their techniques to be more RFC compliant as soon as (if) Yahoo, AOL, Hotmail, Gmail adopted this method.

Your post advocates a

(x) technical ( ) legislative ( ) market-based ( ) vigilante

approach to fighting spam. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.)

( ) Spammers can easily use it to harvest email addresses
( ) Mailing lists and other legitimate email uses would be affected
( ) No one will be able to find the guy or collect the money
( ) It is defenseless against brute force attacks
(x) It will stop spam for two weeks and then we'll be stuck with it
( ) Users of email will not put up with it
( ) Microsoft will not put up with it
( ) The police will not put up with it
( ) Requires too much cooperation from spammers
( ) Requires immediate total cooperation from everybody at once
(X) Many email users cannot afford to lose business or alienate potential employers
( ) Spammers don't care about invalid addresses in their lists
( ) Anyone could anonymously destroy anyone else's career or business

Specifically, your plan fails to account for

( ) Laws expressly prohibiting it
( ) Lack of centrally controlling authority for email
( ) Open relays in foreign countries
( ) Ease of searching tiny alphanumeric address space of all email addresses
(x) Asshats
( ) Jurisdictional problems
( ) Unpopularity of weird new taxes
( ) Public reluctance to accept weird new forms of money
( ) Huge existing software investment in SMTP
( ) Susceptibility of protocols other than SMTP to attack
( ) Willingness of users to install OS patches received by email
( ) Armies of worm riddled broadband-connected Windows boxes
(X) Eternal arms race involved in all filtering approaches
( ) Extreme profitability of spam
( ) Joe jobs and/or identity theft
( ) Technically illiterate politicians
( ) Extreme stupidity on the part of people who do business with spammers
(x) Dishonesty on the part of spammers themselves
( ) Bandwidth costs that are unaffected by client filtering
( ) Outlook

and the following philosophical objections may also apply:

( ) Ideas similar to yours are easy to come up with, yet none have ever
been shown practical
( ) Any scheme based on opt-out is unacceptable
( ) SMTP headers should not be the subject of legislation
( ) Blacklists suck
( ) Whitelists suck
( ) We should be able to talk about Viagra without being censored
( ) Countermeasures should not involve wire fraud or credit card fraud
( ) Countermeasures should not involve sabotage of public networks
( ) Countermeasures must work if phased in gradually
( ) Sending email should be free
( ) Why should we have to trust you and your servers?
( ) Incompatiblity with open source or open source licenses
( ) Feel-good measures do nothing to solve the problem
( ) Temporary/one-time email addresses are cumbersome
( ) I don't want the government reading my email
( ) Killing them that way is not slow and painful enough

Furthermore, this is what I think about you:

(x) Sorry dude, but I don't think it would work.
( ) This is a stupid idea, and you're a stupid person for suggesting it.
( ) Nice try, assh0le! I'm going to find out where you live and burn your
house down!

Re:Oblig. (0)

Anonymous Coward | more than 7 years ago | (#17719144)

Poor Spam, The canned meat will always have a poor reputation cause of these posts.

Re:Oblig. (3, Insightful)

um... Lucas (13147) | more than 7 years ago | (#17719150)

If i had mod points, I'd say you were insightful... Instead, I can only chime in, agree and say "well, now that those instructions are posted, surely it'll just be a day or a week until spammers work around that. So, nice idea, not much of a future, I don't think...

MOD PARENT UP +5 THE FUNNAH (1)

hirschma (187820) | more than 7 years ago | (#17719178)

Just an awesome post. Love it.

Re:Oblig. (4, Interesting)

AchiIIe (974900) | more than 7 years ago | (#17719206)

in response to:
> (x) It will stop spam for two weeks and then we'll be stuck with it

There is another anti spam technology called (doubleverify?), if a message smells like spam the smtp server rejects it saying unavailable and waits for the sender to send it again (an hour or so later). For people who use it it works fine, but people who use it are in the minority, thus spammers won't bother writing new systems that keep track of what was rejected etc. They appeal to the (cheap) masses.

Same here, unless this becomes widely popular few spammers will adopt it. Thus there's a chance for this to work (hopefully, unlike doubleverify this is not patented)

Re:Oblig. (1)

Whiney Mac Fanboy (963289) | more than 7 years ago | (#17719256)

if a message smells like spam the smtp server rejects it saying unavailable and waits for the sender to send it again (an hour or so later).

Great. Lots of emails delayed for an hour, lots of emails lost due to non-rfc compliant sender. Doubleverify are welcome to the patent on that utterly useless (in the real world) idea.

Re:Oblig. (1)

Herby Sagues (925683) | more than 7 years ago | (#17719806)

If an SMTP sender is non RFC compliant, I would suggest dropping the message. It is about time we start discouraging the usage of crappy senders.

Re:Oblig. (2, Insightful)

Whiney Mac Fanboy (963289) | more than 7 years ago | (#17719872)

If an SMTP sender is non RFC compliant, I would suggest dropping the message. It is about time we start discouraging the usage of crappy senders.

Fine in principal, not so fine if the non-compliant SMTP sender belongs to a client of yours sending a $important_financial_email.

Re:Oblig. (4, Funny)

geminidomino (614729) | more than 7 years ago | (#17720010)

If you do business with clients who send $important_financial_information over inherently insecure and unreliable protocols, you have bigger problems than spam.

That's "greylisting". (5, Informative)

khasim (1285) | more than 7 years ago | (#17719308)

"Greylisting" is where an SMTP server refuses messages for a certain amount of time. You set the criteria on why the message would be refused and how long the server would refuse to accept it.

It's been pretty much defeated now because so many spammers have their machines try to hammer the message through until it does go through.

I'm using greylisting right now and the only advantage is that many times a spammer will end up on an RBL during the 15 minutes that I'm refusing his messages.

Remember, the spammers have, effectively, unlimted bandwidth and unlimited processing power at their disposal.

Re:That's "greylisting". (5, Interesting)

Anonymous Coward | more than 7 years ago | (#17719664)

Just an aside on greylisting: I run a large mail server and we WERE using greylisting. However we have found that many firewalls and anti-spam appliances that act as email proxies cannot respond to the 451 or 421 "try again" response used by greylisting. The appliances bounce the message back to the sender reporting it as a server failure. Unfortunately, this user group includes an ever growing number of goverment agencies and public schools. My best guess is that these appliances have no way to store the message should the first attempt at delivery fail.

I sincerely doubt that most of them would ever try more than the primary MX when delivering mail either.

Non-complience with the standards by email handling programs just makes it easier for the spammers by taking away a postmasters anti-spam tools :-(

Yep Funny (4, Funny)

keeboo (724305) | more than 7 years ago | (#17719376)

Standard Smartass Form for Comments on SPAM

1. Please select format:
( ) In soviet Russia .... you! Kind of joke
(x) The same old form on spam subject we're tired to see here
( ) Some comment on female parts
( ) Suggesting you/slashdot_readers are virgins
( ) Will it run Linux?
( ) Cowboy Neal

2. Are you:
(x) Meant to be funny
( ) In a bad day, trolling
(x) Being authoritative on this subject
(x) Expecting to be modded up
( ) Agreeing with the news
(x) Trying to piss over something people might think it's interesting or relevant

3. Include "I'll be modded down for this but...."? (Y/N)
No

Thank you for submitting your message to the Slashdot forum.
Slashdot Quick'n'simple Form: The easy way to show people how smart your are!

Re:Oblig. (2, Funny)

Triode (127874) | more than 7 years ago | (#17719404)

You must be the fastest typist in the known universe...

We will later have to google: how to type a three page long sarcastic remark in such
time as to still be able to submit it to a /. posting and have it be first post.

You are commended, but for what we have no idea.

Re:Oblig. (2, Informative)

scottv67 (731709) | more than 7 years ago | (#17719630)

You must be the fastest typist in the known universe...

Whiney Mac Fanboy is a subscriber. They (subscribers) get to see the articles before us mortals. First post isn't hard when you can reply to the article before the article is available to the unwashed masses.

Obligatory: Oblig. (1)

dch24 (904899) | more than 7 years ago | (#17719706)

Uh, they can't reply until the article goes live. And they aren't given any information on when it goes live. So he had to sit there and hit refresh and drive up page views just like anyone else would.

Sorry, that wasn't meant to be a rant.

Re:Obligatory: Oblig. (1)

scottv67 (731709) | more than 7 years ago | (#17719776)

Thank you for setting me straight on that point. I am not a subscriber so I assumed that the ability to "preview" articles also included the ability to post replies before the rest of us.

We have to give Whiney Mac Fanboy props for having that monstrous first post locked-and-loaded so he could post the second the article was released.

Re:Obligatory: Oblig. (1)

Whiney Mac Fanboy (963289) | more than 7 years ago | (#17719936)

We have to give Whiney Mac Fanboy props for having that monstrous first post locked-and-loaded so he could post the second the article was released.

Only the first paragraph was mine, the rest was copied & pasted (with X's filled in).

Address Book (2, Interesting)

iendedi (687301) | more than 7 years ago | (#17719470)

How hard would it be for Yahoo, Google and other internet mail services to simply have two inboxes?

One for mail addressed to someone in your mailbox.

One for everyone else.

90% of my spam problem would be solved by this simple recipe.

Re:Address Book (1)

SScorpio (595836) | more than 7 years ago | (#17719638)

Do you mean mail sent from someone in your address book? Addressed to someone in your mailbox does not make sense for Yahoo and Google.

For a domain not having the catch all enabled remove a huge amount of spam though.

Re:Address Book (4, Interesting)

dgatwood (11270) | more than 7 years ago | (#17719978)

Flowchart:

  • in addressbook: goto NOTSPAM.
  • address present as envelope sender in any incoming mailbox: goto NOTSPAM
  • address present as recipient in any outgoing mailbox: goto NOTSPAM
  • address has ever been present as envelope sender in any incoming mailbox:
    • at least one of those messages was flagged as spam: goto SPAM
    • none were flagged as spam: goto NOTSPAM
  • goto SUSPECT

Re:Oblig. (1)

erroneus (253617) | more than 7 years ago | (#17719544)

Uhm... I wouldn't be so quick on that.

I'd say a great many of your check marks might have also been said about the "grey listing" technique. I have been using greylisting for a relatively short time (about two months) but the results have been more than remarkable. This technique certainly warrants a slightly better evaluation than the one you provided above.

Greylisting works for exactly the same reasons this other technique purports -- by utilizing a standard of behavior that real mail servers are supposed to follow that spammers aren't likely observe.

I don't plan to activate any such NoListing configuration any time soon, but it's certainly an interesting idea and merits watching.

Re:Oblig. (4, Insightful)

jon787 (512497) | more than 7 years ago | (#17719608)

Don't have numbers to back it up, but most things I read say that the Secondary MX is *more* likely to be targeted by spammers on the belief that fewer filters will be in place to prevent spam.

Those statements could be refering to their use as open relays though.

Re:Oblig. (-1, Troll)

bergeron76 (176351) | more than 7 years ago | (#17719620)

Wow, your post looks remarkably well prepared for being FP.

Perhaps you're either:
A) the AC that posted it
B) a shill
C) a spammer

Here's what I think about your post:
A) it sucks
B) have a nice day
C) fuck your mother and A and B.
D) all of teh above

Re:Oblig. (1)

scottv67 (731709) | more than 7 years ago | (#17719650)

Wow, your post looks remarkably well prepared for being FP.

You forgot option D

D) A Slashdot subscriber who gets to read the articles (and comment on them) before the articles are released to the great unwashed masses.

Re:Oblig. (1)

scottv67 (731709) | more than 7 years ago | (#17719802)

Please ignore my comment about subscribers. A post higher up explains that although the subscribers can read the articles before the rest of us, they can not reply until the article is released.

Stopping Spam (1)

fyngyrz (762201) | more than 7 years ago | (#17719740)

There is a way to stop spam. It's simple, too. Stop using direct email - don't give out an email address. Ever.

Next time around, we need to develop a technology so that it isn't open to everyone and their brother, his 4th cousin, and that guy who knows your 4th cousin and the fellow who took out that guy's trash.

Web-based contact forms that require humans aren't a bad idea for now. You know... "Randomly ordered /which kitten has the string from the yarn wrapped around its ear?/" one time, and "/which alligator has one eye closed/" in the next, and so on for many, many examples where each image contains considerable random cruft so that they can't be checksummed or etc and marked by a human for a one-time recognition a machine can use. Until Ai comes, that'll work for incoming message traffic if you do it well. Give 'em a URL where your answer will be posted when they send it, and they can check there for an answer if they're so motivated. A program could manage that without being annoying.

'course, then you need a website. Sigh. yeah, what we need is a whole new technology. Key based.

Temporary Solution (5, Insightful)

PhotoGuy (189467) | more than 7 years ago | (#17719142)

This strikes me as the ultimate in temporary solutions. If spam senders *tend* to use only the primary MX record, and people start fighting spam by listing bad primaries, won't the spam senders simply start using secondaries? It almost seems the only way that this approach might be valuable, is if it weren't publicized and posted on /., and one kept it to oneself :)

Re:Temporary Solution (3, Interesting)

TheSkyIsPurple (901118) | more than 7 years ago | (#17719288)

It amuses be a bit. I have the ultimate in no listing for one of my domains. =-)

I used to received about 6 million spams a day across 3 relays for this domain.
I removed all MX records for the domain, and the hostnames have nothing to do with the domain (so A record lookups won't help), but 30 days later I still was receiving over 2 million spams a day. After about 6 months the number really started falling off.

Re:Temporary Solution (1)

TheLink (130905) | more than 7 years ago | (#17719646)

How do you receive 2 million spams a day after 30 days with the domains off? You temporarily put them back on to check?

If you are really no longer using those addresses for communications, you could use them as a spam canaries.

Increase the spam "score" of any message that goes to those addresses. If it's multiple "unrelated" addresses then it's even more likely to be spam.

The spammer has to somehow detect this or send more unique emails - which slows them down.

Re:Temporary Solution (2, Informative)

TheSkyIsPurple (901118) | more than 7 years ago | (#17719926)

The kept the IPs handy, not even bothering to check DNS.

I handled other domains on the same servers, so I'd still see the requests come in

Re:Temporary Solution (2, Interesting)

adrianmonk (890071) | more than 7 years ago | (#17719710)

I removed all MX records for the domain, and the hostnames have nothing to do with the domain (so A record lookups won't help), but 30 days later I still was receiving over 2 million spams a day. After about 6 months the number really started falling off.

It's not hard to think that spammers are probably keeping lists of IP addresses rather than DNS names. They don't care about correctness, so there is no need for them to try the correct SMTP server. Therefore, why bother with the overhead of DNS? Or at least, why do the lookup more than once every month or so, especially when IP addresses of mail servers tend to be pretty stable. (You might even call them "static".)

Because spammers may be directly targeting an IP address, one other possible way to fight spam is to change the IP address of your SMTP server regularly. If you change the MX records (well, really the A records they point to), legitimate traffic will pick up the changes. To be safe, you can continue to listen on the old IP address for a week or so while you make the transition to the new IP address. That ought to give stale DNS entries plenty of time to expire.

And, of course, you keep rotating, so that out of, say, 254 possible addresses, you're only using each one for maybe 1% of the time. The other addresses are, of course, not responding to any TCP packets received on port 25.

All this will achieve in the long term is force spammers to use DNS and/or carefully prune their list of IP addresses they try to send spam directly to. Well, that and any message sent to an IP address that hasn't been current for, say, 1 month is a message that is a very strong candidate for being sent to an RBL.

It's not a huge win, and the spammers will adapt, but until someone figure out some idea which is a huge win, there is some value in continuously forcing spammers to adapt. It makes spamming less easy.

Spammers often try secondary MX's. (4, Insightful)

khasim (1285) | more than 7 years ago | (#17719340)

Spammers will often try secondary (and lower) MX's because there's a good chance that the anti-spam AND ANTI-VIRUS systems on those machines are weaker (read "outdated") than on the primary MX.

The more machines you have to maintain, the more likely you are to focus your efforts on the most critical ones and just let the other slide. Spammers are happy to exploit this.

Re:Temporary Solution (2, Insightful)

httpdotcom (749192) | more than 7 years ago | (#17719342)

The interesting thing about the solution is that it will increase costs for the spammer. Their MTA's will either dump the original mail, as it is not configured to handle secondary MX records (non-RFC compliant sender) or it will spend the cycles that would normally be used sending other messages. While the bounces could be shuffled off to servers designed specifically for the purpose of fighting this approach, it is still a win against spammers, in the short term.

Re:Temporary Solution (2, Informative)

bigberk (547360) | more than 7 years ago | (#17719506)

The interesting thing about the solution is that it will increase costs for the spammer.
Not quite, because spammers don't really pay for bandwidth. They steal the computing power and bandwidth from victims (virus infected machines) to set up botnets, and then leverage the stolen resources for their marketing business.

Re:Temporary Solution (1)

jelle (14827) | more than 7 years ago | (#17720008)

"They steal the computing power and bandwidth from victims (virus infected machines) to set up botnets, and then leverage the stolen resources for their marketing business."

Which brings us to the real cause of the spam problem. The receiving end is the victim, not the cause. The problem is the large amount of easily infected windos machines with mass-email sending capabilities.

Re:Temporary Solution (2, Insightful)

ocbwilg (259828) | more than 7 years ago | (#17719656)

The interesting thing about the solution is that it will increase costs for the spammer. Their MTA's will either dump the original mail, as it is not configured to handle secondary MX records (non-RFC compliant sender) or it will spend the cycles that would normally be used sending other messages. While the bounces could be shuffled off to servers designed specifically for the purpose of fighting this approach, it is still a win against spammers, in the short term.

Not only do most spammers not pay for bandwidth (stealing it from broadband connected zombies instead), but most legitimate businesses do pay for bandwidth. So you're actually increasing the onus on all email servers in order to get a temporary reduction in spam, which will be reversed as soon as the spammers start programming zombies to try all MX servers listed. Not to mention the additional delay that retries on subsequent MX servers can introduce in mail delivery. People complain as it is if they have to wait 5 minutes for an email that someone sent them.

Re:Temporary Solution (3, Funny)

Frogbert (589961) | more than 7 years ago | (#17719452)

Thats why we all have to keep wraps on this idea. Don't tell anyone. It's much like Usenet, don't talk about it and everyone in the know benefits.

Re:Temporary Solution (0)

Anonymous Coward | more than 7 years ago | (#17719530)

One interesting thing to note. If most spammers use the same approach it is likely most spammers use the same software and perhaps even originate from the same small set of spammers. If you could track down those spammers and shut them down, there would be a huge decrease in the amount of spam.

Short Term Solution (5, Insightful)

pyite (140350) | more than 7 years ago | (#17719166)

This is not a long term solution.

1) It's bad netiquette, and a lot of people don't like that, including myself and I'm sure many other administrators.
2) It's an artificial "defense" that is easily circumvented because the rule is obvious. It's security through obscurity with the added suck that there is no obscurity.
3) It's solving a symptom and not any of the actual problems (e.g. hosts being compromised to send spam).

Thanks, but I'll pass.

Re:Short Term Solution (1)

erroneus (253617) | more than 7 years ago | (#17719680)

Given that there is NO 100% true solution to the problem, things have to be done... or at least tried. Greylisting could be counted in the same numbers that fit the reasons you list above, but it works remarkably well.

I'm sure you advocate murdering the spammers for their deeds... (I don't though I quietly hope to see headlines to that effect in the daily news) but expecting marketers to "follow ettiquette" ain't gonna happen. At all professional levels, the same basic abandon of moral and ethical standards exists in large amount.

Ultimately, until spammers are equated with "terrorists" then it won't be actively punished. After all, there are many Fortune 500 companies that utilize email campaigns to advertise... hell a company I used to work for routinely blasted out emails to clients only to find themselves constantly being blocked by spam lists... which then interfered with normal emailing activities. No amount of explaining the negative impact would deter the marketting people from wanting to do this. They're thoughtless assholes with one goal in mind: to make a profit.

funny (3, Funny)

User 956 (568564) | more than 7 years ago | (#17719172)

An anonymous reader writes with the technique of Nolisting, which fights spam by specifying a primary MX that is always unavailable.

Funny, I fight afternoon meeting schedulings in almost the same way. Just specify a primary time that's always unavailable.

OT - Re:funny (3, Funny)

proverbialcow (177020) | more than 7 years ago | (#17719370)

Funny, I fight afternoon meeting schedulings in almost the same way. Just specify a primary time that's always unavailable.

When I worked overnights, I had a similar system.

Boss: We need to talk.
Me: Great. What night would you like to come in?
Boss: No, I mean you should stay late.
Me: But you don't come in until 9, and my shift ends at 7.
Boss: But it's important!
Me: Why is it always about your needs. Your need to have a meeting. Your need to get a decent night's sleep. What about my need not to sit around for two hours on the clock waiting for you to show up, surfing the web, all the while getting paid one-and-a-half my regular pa...okay, fine, you win.

Then, when I became the boss years later, I would always show up at the beginning of the night shift to talk to the employees, and then go to the bar. It made the employees feel noticed and made my superiors think I was motivated. Turns out my best defense against assholes like me is actually having been me.

hmmm (1)

jonpublic (676412) | more than 7 years ago | (#17719174)

As someone who runs the incoming mail machines for a large university, I have found that spammers pick the highest and lowest IP to hammer away on, regardless of MX preference. Many spammers specifically target the high MX. I fail to see how making the low mx unavailable will deter spammers. If they can alter each image they send with each spam, they can alter which IP/MX their botnets deliver to.

Re:hmmm (2, Interesting)

Anonymous Coward | more than 7 years ago | (#17719306)

it makes sense as a spammer to hit the secondary MX anyway as *most* secondaries don't know anything about the mail accounts themselves, but rather just spool and relay the domain onto the primary. with this in mind the secondaries will nearly always accept mail for any account in the domain, say 'thankyou very much' to the SMTP client and go about managing its local queue for delivery, hammering away at delivery attempts on the primary and then filling up the secondary queues trying to send the bounces back to bogus return paths, so i'm not sure i understand how nolisting is anything *but* a band-aid solution.

as a spammer writing your own SMTP engine, why wouldn't you just write in basic queue management into your client to get around nolisting/greylisting/nastyhacklisting...?

I run a mailserver, this is a bad idea (4, Insightful)

Gothmolly (148874) | more than 7 years ago | (#17719176)

We get stuff directed at our secondary all the time, despite having a highly available primary. Why? Our secondary is listed at another domain - they do our backup in the case of disaster. I can only assume that spammers hit it thinking that its a 'back door' into the network, perhaps we don't have the same rigorous anti-spam measures there.

Dumb idea. You're better sending all your domain mail to gmail, using their spam filtering, and then pulling it from there.

I run a high volume mailserver, this is a bad idea (4, Interesting)

chathamhouse (302679) | more than 7 years ago | (#17719434)

I run a mail system that pushes ~3million messages per day. Not huge, not small.

We have thousands of domains pointed to our mail servers and secondary MX servers. Looking at the long run stats, I'd be tempted to completely disregard this technique.

When we take a primary down for maintenance, the secondaries and alternate primaries (same weight MX) see the load almost immediately.

I second the opinion that if this has any effect, it's only for low volume applications, with few/one domain.

We generally see more hits straight to the secondaries by spammers hoping for less rigorous checking. It would be interesting to profile IPs connecting to secondaries without being seen at the primary assuming a primary is always available - I bet that a very high percentage of these connections to secondaries could be viewed as spam.

The problem remains that most tricks of this sort - including greylisting - are eventually circumvented by spammers once the trick gains critical mass. Lets not forget that there are a lot of broken, yet not open relay, mail servers out there. Good engineers and administrators quickly find that Jon Postel's words ring true with their customers "Be liberal in what you accept, and conservative in what you send." - don't let your RFC enforcing configuration be responsible for delaying/blocking the delivery of that big contract your PHB was waiting for!

Um (0)

Anonymous Coward | more than 7 years ago | (#17719182)

Greylisting [wikipedia.org] works just as well, donkeys.

Re:Um (1)

Ash-Fox (726320) | more than 7 years ago | (#17719194)

When I used it, spam still got through, some legitimate mail didn't.

Re:Um (1)

erroneus (253617) | more than 7 years ago | (#17719720)

It's true... some servers need to be white-listed because either they resend from a different IP or just never make second attempts. They are few and generally well-known though.

Re:Um (1)

Uzik2 (679490) | more than 7 years ago | (#17719310)

I use greylisting and it works very well for cutting down on the spam.
I do about as well as gmail and better than yahoo.

Won't work. (5, Insightful)

schon (31600) | more than 7 years ago | (#17719184)

Most spam bots already send to the *lowest* priority MX (ie. the highest number), and work their way backwards, because it's common for the backup MX'es to have lower anti-spam rules.

However, this idea would have been *great* six years ago. Once the developer invents a time machine, he's got the spam problem licked for at least a week!

Re:Won't work. (0)

Wizarth (785742) | more than 7 years ago | (#17719330)

This is what I came in to say, thank you.

Re:Won't work. (1)

dzelenka (630044) | more than 7 years ago | (#17719430)

Ditto.

I believe my secondary MX sees more spam than my primary already. I'd have to see some stats to change my mind.

Re:Won't work. (1)

slamb (119285) | more than 7 years ago | (#17719518)

Most spam bots already send to the *lowest* priority MX (ie. the highest number), and work their way backwards, because it's common for the backup MX'es to have lower anti-spam rules.

Do you have any experimental results to back up your claim? Any actual reason to believe it's true? Because he has results that dispute it. Read the article. In his quick experiment, 47% of confirmed spammers tried the primary only, 36% tried the secondary only, and only 17% tried both. While possible that his sample is skewed or that spammers have adapted since his experiment was performed (page was Last-Modified: Sun, 12 Nov 2006), I'm much more inclined to believe the guy who has done his homework over the guy shooting from the hip on slashdot.

The only real objection I've heard on slashdot is that spammers will adapt. Could be true. The author thinks his technique will never be common enough for spammers to bother adapting to, but they may alter this behavior as a side effect of adapting to more common techniques like grey-listing.

I think I'll give it a try. It's trivial to set up and has an extremely low risk of losing legitimate mail. If it doesn't work, I've lost only a few minutes of time.

Re:Won't work. (2, Informative)

schon (31600) | more than 7 years ago | (#17719674)

Most spam bots already send to the *lowest* priority MX
he has results that dispute it.
If he does, he didn't post them to his page.

If you take a look at his page, he says that he used DNSBL.

DNSBL host != spam-bot

Spam-bots are a subset of the hosts that would be listed in a DNSBL.

Next time, before attacking someone, you might want to work on your reading comprehension skills. You'll look like much less of a fool.

Re:Won't work. (1)

wytcld (179112) | more than 7 years ago | (#17719704)

I wonder what our variability is as spam targets. I've seen spam drop markedly with greylisting just on the primary MX. But I can't give a good statistic because I implemented another change at the same time. I'd always set domains up with a catchall that sends unspecified userids to a mailbox, and it's gotten to where for domains that have been around for some years most of the spam coming in is addressed to fake addresses that have been created evidently by other spam faking being from the domain, and then harvested somewhere. Since I've also handed out addresses like amazon@domain.com to track merchants who leak addresses, can't remember them all but still want some of that merchant mail, just sending all this to /dev/null isn't the answer. Ah, but for whatever reason the bulk of the spammed fake userids are addressed to userid@sub.domain.com (legitimate subdomain names from my DNS records). Between tossing all addressed to a subdomain and greylisting, spam has dropped by 90% even with a secondary MX that doesn't greylist.

But the array of spammers that target me and those that target someone else may well differ greatly. Maybe someone else gets heavily spammed by secondary-MX targeters even though I'm not.

STUPID IDEA! (-1, Redundant)

Anonymous Coward | more than 7 years ago | (#17719222)

My backup MX's are more commonly targetted than my primary MX's

This is bullshit! (2, Funny)

LibertineR (591918) | more than 7 years ago | (#17719230)

How many solutions do we have to implement before Spam is outlawed? Why is this shit allowed to go on, stealing bandwidth and all?

There is more spam than penises needing enlargement, dammit!

I cant believe this is allowed to go on. How long did it take for callerID and no-call lists to get here? How long before we start putting these people in jail!

No more bandaids, lock these fuckers up!

Re:This is bullshit! (0, Flamebait)

/dev/trash (182850) | more than 7 years ago | (#17719322)

You want to outlaw free speech?

Re:This is bullshit! (2)

rblum (211213) | more than 7 years ago | (#17719372)

Yawn. Not that old saw. Spam is not free speech - it's commercial speech, which has always been regulated. Hint: "Free Speech" does not mean that you can say whatever you want, whenever you want.

Re:This is bullshit! (1)

HexRei (515117) | more than 7 years ago | (#17719476)

No, but I get plenty of physical spam mail, and I try not to put my address on anything if I can avoid it. Sure, you can make it illegal to keep sending to a recipient after being asked to stop, but the sheer cost and bureaucracy of investigating every case will make it moot.

Re:This is bullshit! (3, Insightful)

LibertineR (591918) | more than 7 years ago | (#17719422)

Idiot!

Spam is NOT free speech. You cant come into my home screaming penis ads at me without getting your ass kicked, so why should you be able to do it into my mail server?

Re:This is bullshit! (0, Flamebait)

Elemenope (905108) | more than 7 years ago | (#17719772)

You need not open your mail, esp. when the subject line is something that you aren't interested; it is the same filtering methodology one uses for snail mail, by checking the return address and other identifying markers on an envelope before deciding whether or not to bother opening it or just tossing it. Difference is, you can do the toss action with two clicks online, whereas it is a more extensive process in meatworld. Heck, its even easier with 'spam filters' that do 80% of the work for you.

Thus, there is no 'screaming penis ads in home'; it's a poor and deceptive metaphor. And, yes, advertising generally is free speech. I'm no great fan of spam (in point of fact, I hate it) just as I dislike most modern advertising in general, but it does seem to be a latent unavoidable consequence of valuing free expression in a product-value based society. I deeply love my right to express myself, and often enjoy the way others put that right to use as well.

Re:This is bullshit! (1)

localman (111171) | more than 7 years ago | (#17719920)

I believe in free speech when the technology used is "pull" instead of "push". Does that make sense? I believe you have the right to say whatever you want to whomever you want if they are willing to listen, but I also have the right to not have to listen. I should be able to say "stop bothering me" and have that respected.

And unfortunately spam is not just an issue of "don't open the message". Many messages don't have helpful subject lines, instead opting for "Re: your mail" or somesuch. And if you have any public interactions, you don't get all your messages from people you already know. I get over 700 spam messages per day, this gets in the way of me doing my responsibilities. I am lucky in that I am tech savvy enough to have set up sophisticated spam filtering (so only 5 or so a day get through), but the original poster is right: it is illegal to call someone's home after you've told them not to. Nearly all direct marketers will stop sending snail mail if you ask (if not, I'm sure there would be a law about that too). Spam is harassment, not free speech.

Cheers.

Re:This is bullshit! (1)

erroneus (253617) | more than 7 years ago | (#17719770)

You have a right to free speech, but you DON'T have a right to be heard. In other words, you cannot use forceful or otherwise subversive methods to "ensure your speech is heard." If someone doesn't want to hear it, that take precedence over anyone's right to free speech.

And commercial or other such activities do not count as speech in the sense that most people consider. .../dev/trash indeed...

Re:This is bullshit! (1)

RexRhino (769423) | more than 7 years ago | (#17719402)

Because enforcing laws against spam are like enforcing laws against oral sex. How exactly do you plan to track down and punish lawbreakers without big brother style surveillance?

Re:This is bullshit! (1)

alister (60389) | more than 7 years ago | (#17719514)

Because enforcing laws against spam are like enforcing laws against oral sex. How exactly do you plan to track down and punish lawbreakers without big brother style surveillance?

A lot of spam is aimed at getting money. So, follow the money (hey, that sounds like a good catchphrase).

Re:This is bullshit! (1)

jeff4747 (256583) | more than 7 years ago | (#17719762)

A lot of spam is aimed at getting money. So, follow the money (hey, that sounds like a good catchphrase).

And when you start doing that, here's what you'll hear:

"I'm sorry, the government of Angola refused to serve your search warrant. Your money trail hit a dead end."

You can only reliably follow the money within one country's legal system. As such, spammers would simply move part of their money trail into another country and continue to spam. Without the ability to actually follow the money trail you can't go after the money when it comes back to the US (or whatever country you are in).

How long? (1)

Vitriolix (660279) | more than 7 years ago | (#17719474)

> How long did it take for callerID and no-call lists to get here? About 125 years

Re:This is bullshit! (1)

Xybot (707278) | more than 7 years ago | (#17719522)

"There is more spam than penises needing enlargement, dammit! " Can you forward me some of yours? the first couple I tried didn't work too well

Their customers are the ones at fault here. (2, Interesting)

Anonymous Coward | more than 7 years ago | (#17719542)

Like it or not, these spammers run extremely profitable businesses. You may not realize it, but they can only continue doing what they're doing because enough people actually do happen to buy the products that they advertise via spam. If people stopped buying items advertised in that way, then the spammers would have no market to sell to, they wouldn't make money, and thus would have virtually no reason to send out spam.

A number of recent studies have shown that most of the major purchasers of goods advertised via spam are from the United States. One particular report offered statistics showing that most spam-advertised goods were bought by people in the Oklahoma, Arkansas, Mississippi, Alabama, Tennessee and Missouri region of the US. Another major area for the purchasers of spam-advertised items was London, England.

If anyone is responsible for spam, it is all the people who actively go forth and continually buy the items that are advertised via email spam.

Re:Their customers are the ones at fault here. (1)

erroneus (253617) | more than 7 years ago | (#17719852)

You know, I think you're on to something. Here's what I think we need:

We need a method that authorizes a party to conduct business excluding all others. Let's make it something simple like a number on one's forehead or arm or something. It's not my idea though... I think I read it somewhere... like in Revelations or something like that.

It's true that by eliminating the buyers, the sellers would not do business. But there's no practical means to educate buyers. Every buyer knows that cigarettes are disgusting, stinky and harmful to health yet people keep buying them. It's simply better to regulate the sellers.

That said, it would also make sense to elist the assistance of credit card companies through which these people do business.

Jail is hardly the best option. (0)

Anonymous Coward | more than 7 years ago | (#17719716)

How long before we start putting these people in jail!

Hopefully a very, very, very, very long time. Ideally, never. Jail is perhaps the worst possible place to put spammers.

First of all, what they're doing is not at all harmful to society at large. Using a proper mail filtering system, it's quite easy to remove the vast majority of spam. Furthermore, blacklisting, greylisting and whitelisting techniques can be used to prevent spammers from even connecting to your SMTP servers in the first place, hence vastly reducing the load put on them filtering spam, and also reducing the bandwidth that is consumed. The cost to you can basically be eliminated outright.

Second of all, it's fucking expensive to jail even just one inmate. That's why it's best only to jail those who have committed serious crimes. Maybe you don't realize it, but it's the money you pay in taxes that goes towards locking such people up. Frankly, I'd rather delete a few unwanted mails each day, then knowing that the state will be paying $60,000 or more each year to lock that spammer up. A portion of that money is coming directly from my pocket, and yours. That's not something I approve of. I like my money in my pocket.

Then again, you'd have to catch them in the first place. It's unlikely that you'll be getting your American hands on any Russian, Pakistani, Sudanese or Chinese spammers. It'd be a waste of time and resources for such countries to hand over such petty criminals.

Attacks on 2ndary relays (2, Informative)

mcrbids (148650) | more than 7 years ago | (#17719232)

For some time a few years ago, spammers used to IGNORE the primary MX and send to secondary MXs preferentially.

Since in our case, the 2ndary MX was a dumb sendmail relay only without knowledge of the user DB, it shot the traffic load out thru the roof with bounces to junk spam that, because they couldn't be rejected during the actual delivery attempt, hammered our backup relay.

This is just a dumb idea.

Re:Attacks on 2ndary relays (1)

stilwebm (129567) | more than 7 years ago | (#17719336)

I observed this exact behavior. The reason this was done was exactly as you mentioned - many lowest priority MXs are simply for store and forwarding backup and have no knowledge of the user database. This means the spammer can slam the server without getting rejections. That way the bounces go to the foraged address and the spam server's connection can close faster.

Some spammers target secondary MX first (4, Insightful)

straponego (521991) | more than 7 years ago | (#17719244)

...on the assumption that it will be less well-protected than the primary. If many people pull this fake-primary trick, I would assume they'll react quite quickly. This doesn't seem like much of a long-term defense. It looks to me like good defenses will (and do) involve either complex, evolving techniques (think of the p2p/reputation type stuff in razor/pyzor and FuzzyOCR), or hard choices (reject image-heavy messages, whitelist/greylist, etc). No defense, of course, will be perfect.

Based on watching a few corporate spam sites and even stuff which reaches my private, never-posted addresses, *much* of the spam could be eliminated by moving non-Windows clients. I'm not just talking about zombies. Some of the spam I see hits lists of addresses which are valid and include very difficult to guess addresses inside the company. Once somebody inside your company, or a buddy of yours is rooted, your previously private address is out there; I've never had this happen via any route but a Windows user. Of course, people who CC: everybody they know with idiotic crap instead of BCC: make this problem much worse.

Oh, and please stop with the lame form letter responses to these articles. It was cute once, long ago. I know at least five people will have posted them by now. Damn spammers.

Re:Some spammers target secondary MX first (1)

Feyr (449684) | more than 7 years ago | (#17720020)

Of course, people who CC: everybody they know with idiotic crap instead of BCC: make this problem much worse.
and with hotmail not allowing bcc:'s it's just compounding the problem. idiot people posting my private address for all to see :\

Thanks slashdot... (1)

binaryspiral (784263) | more than 7 years ago | (#17719314)

Now the spammers just pushed out an update to their botnets... "Soldiers - try the high MX first."

Okay everyone, switch your primary back - and don't post it on /.

Oh, wait... doh!

Re:Thanks slashdot... (1)

geminidomino (614729) | more than 7 years ago | (#17720056)

And the botnets responded: "We've been doing that for the past 5 years, General."

Should be more like Russia (0)

Anonymous Coward | more than 7 years ago | (#17719334)

Just take the bastard spammers out into the main street and shoot them.
Bet you'd only have to shoot a couple to stop spam completely.

buh (2, Funny)

bitspotter (455598) | more than 7 years ago | (#17719366)

Set the primary MX to 127.0.0.1 . That should keep those buggers busy for a few days. Have fun with those feedback loops, sucka!

Of course, the same might be true of legitimate senders, as well.... ;p

And WHY won't google rent out Gmail's filters? (3, Insightful)

straponego (521991) | more than 7 years ago | (#17719382)

Gmail's filtering is, well, badass. I'd think a large number of companies would be willing to pay them to handle email for their domains and forward to a company mail server which only accepts messages via gmail. You'd get a very nice web interface, but could still have the speed and power of a local POP/IMAP server. And virtually no spam. That would be worth a few bucks a month per account for a lot of people. Me, I'd be a little creeped out by them having that much access to my personal emails. Which is why I only use gmail for stuff that I don't want lost in a spam filter, like job searching, financial transactions, attorneys, my friends traveling in the Middle East, etc. But nothing personal!

Re:And WHY won't google rent out Gmail's filters? (1)

StikyPad (445176) | more than 7 years ago | (#17719712)

I'm not sure what you mean by "badass." My GMail address fares no better than my Hotmail address. If anything, my GMail address (which I have given only to a few friends and potential employers) gets slightly more spam in the Inbox (although less overall). Maybe GMail is just a bigger target because of how highly it (initially) touted its spam-fighting capabilities, but I haven't noticed a significant improvement.

I will say that GMail is less likely to mark a valid e-mail as spam though, from what I've noticed. Not that I've had anything other than a registration confirmation or password reminder marked as spam in Hotmail, and I never provide my GMail address for those, so it's not really a valid comparison.

Re:And WHY won't google rent out Gmail's filters? (1)

Torvaun (1040898) | more than 7 years ago | (#17720050)

I've had the opposite experience. My Hotmail caught approximately 10% of the spam I received. I've had a grand total of 3 spam mails go to my Gmail inbox, and they were all those snippets from literature spams that were trying to desensitize filters.

Opposite of what I've seen (1)

WoodstockJeff (568111) | more than 7 years ago | (#17719432)

Very strange. I've found that spammers try the secondary MX first, hoping that it has lower filtering than the primary. The higher the MX priority, the higher the probability that it will be the FIRST to be hit. That's why my secondary MX records point to the strictest server in our "cluster"... For a while, it pointed to one that refused ALL mail!

Not as good an idea as it sounds (3, Informative)

bigberk (547360) | more than 7 years ago | (#17719486)

This probably works in many cases, but as a mail system admin I can tell you that it can fail and will cause problems for legitimate mail delivery. Over the past few months I remember seeing a few messages stuck in my Postfix mail queue, that didn't ever seem to make it out to the recipient's MX. These were domains with deliberately non-functioning MX, and I could not figure out why Postfix was not trying the other MX even though it was up and running. In one case I also tried mailing the recipient domain through gmail, which ALSO failed after many days of retrying. Again I am not sure why the scheme failed to work, but it did fail through both Postfix and gmail which are two very legitimate mail servers.

Spammers IGNORE the MX priority (4, Insightful)

IGnatius T Foobar (4328) | more than 7 years ago | (#17719504)

Sorry, this isn't going to work. It won't even help a little bit. As a long-time email administrator and the author of an email server I can tell you, with absolute certainty, that spammers ignore the priority of your MX records. In fact, they exploit multiple MX's much of the time, by sending spam to your secondary server(s) even if the primary one is up. In addition to extra target capacity, they often manage to take advantage of badly configured secondaries that might not have spam filtering that's as good as the primary, and in many cases the primary has its secondaries whitelisted to make sure no mail gets accidentally dropped.

What's with the breakage to fight spam? (3, Insightful)

Anonymous Coward | more than 7 years ago | (#17719510)

How comes everyone tries to fight spam by breaking infrastructure? Wikipedia neuters links, email server admins delay mails (graylisting) or even reject connections (unlisting), users turn off Flash and Javascript to avoid ads. IMHO, if we have to break our own toys to keep the spammers from playing with them, we're heading for dull times.

Re:What's with the breakage to fight spam? (2, Insightful)

robogun (466062) | more than 7 years ago | (#17720006)

This is the Tragedy of the commons [wikipedia.org] , a result of selfish use of a common resource by selfish individuals. It's not just spammers and marketers: If my server is getting pounded I might have to take an arguably selfish action by withdrawing it.

I like to think there's an answer out there in game theory, but with the players numbering in the hundreds of millions if not billions, may be unsolvable.

They will respond (3, Interesting)

btempleton (149110) | more than 7 years ago | (#17719532)

But they're often slow to respond. Hell, I changed a DNS record when I moved servers once and spammers will still going after the other server, with no DNS record pointing to it, for 6 months because they use static caches.

Many people were already using this trick, probably hoping it wouldn't show up as lead story on slashdot.

In some ways, selfish ways, it's like the story of the two hikers who face a bear. The first hiker immediately sits down and starts putting on his running shoes. The other says, "What are you doing? You can't outrun the bear!" The first hiker says, "I don't have to outrun the bear. I just have to outrun you."

Many spammers, faced with a failed attempt at sending mail, do not bother to retry or try other MX. Instead, they just move on to the next target in the list, since trying a new target is just as easy as retrying an old target. No real difference to them. But it means you just push your spam attempts onto other people who haven't elected to bend the standards to divert the spammers.

The "good" spam sending programs run many threads, timeouts don't punish them, their limit is more the bandwidth. Attempts to divert spammers onto others who have not tried the tricks should create an ethical question. Are we just arranging for the bear to eat our friend?

The only solution... (2)

arthurpaliden (939626) | more than 7 years ago | (#17719632)

ISPs must restrict clients to 'n' emails (ie free minutes) per day based on their type of account. If they want to send more they have to pay.

"The only solution..." isn't. (0)

Anonymous Coward | more than 7 years ago | (#17719868)

No. That's not the only solution. It's not even the best ISP-managed solution. A much better one is to disable port 25 on most internet broadband internet connections, and ALL connections with a dynamic IP. Exceptions to this rule would be granted to anyone who explicitly requests to have port 25 open because they are running a server.

Most spam comes from botnets these days. And the bots are generally running on unpatched compromised home or work machines. Machines that have no business sending traffic on port 25. Just block the bloody stuff.

Just like MailHurdle (1, Informative)

jonnythan (79727) | more than 7 years ago | (#17719718)

It sounds like a function called MailHurdle that's built into Mirapoint email filters.

It works wonderfully. We've been using for about a year at my organization. It works by initially rejecting all incoming mail from unknown servers. If the server is legit, it will retry the email, and on that retry, MailHurdle will allow the mail through.

It instantly eliminated well over half of our incoming spam. Very clever technique, and it certainly works.

Spammers and MX records (2, Interesting)

networkzombie (921324) | more than 7 years ago | (#17719730)

I have an IP that still receives spam even though the MX record was changes seven years ago. That's right. SEVEN YEARS. Every once in a while I monitor port 25 and sure enough after about five minutes a hit, then another and another. There has been no SMTP for seven fricken years and they are still trying. Anyone who thinks spammers abide by MX records and RFCs is smoking crack.

For all the people saying spammers use the 2nd.... (0)

Anonymous Coward | more than 7 years ago | (#17719736)

Then make the 2ndary MX the bad one!

Solution to SPAM is much simpler. (0)

siyavash (677724) | more than 7 years ago | (#17719782)

I said it before, and I'll say it again :

SPAM ? I haven't seen "SPAM" for over 7 years now. While you stupid morons keep fighting to get rid of it, I have managed to find the perfect solution. and I mean this is 100% secure. ( I have copyright on this by the way ).

See, an email is like opening your door in a city, any hobo can just open the door and look inside your home. My solution is to create different doors for every person out there.

How ?

With email aliases.

You can't do this with gmail or whatever ( Although, IF Google TRUELY wanted to eliminate SPAM, they would allow you to have some sort of email aliases aka youraccount.aliases@gmail.com ). You need to first buy your own domain where you are able to create *@domain.com aliases.

Now, once you have that, everytime you publish your email somewhere you create an alias for that "somewhere". For example, if you want to give your email to slashdot, you create an alias "slashdot" and your email will be "slashdot@mydomain.com". Then, if you want to give away your email to amazon, you do "amazon@mydomain.com"... etc.

See my point ?

This way, once you start getting SPAM, Two HUGE benefits :

1. You know for sure, 100% WHERE the SPAM is comming from and which one of your aliases are infected. As in, who sold you out!

2. All you need to do is to just close that alias. and *poof*, no more SPAM from there. All the other aliases are safe and you won't have to worry about losing emails.

and if wanna put your email on a website ? Use a mailform.

I'm amazed that google or microsoft have not come up with such solution, one could have mygmailaccount.alias.@gmail.com for example to give away, this way one would be able to shut that alias down once it gets SPAM infected.

Now, while you waste your CPU and TIME on getting rid of SPAM, I'll enjoy a 100% SPAM free email experience without tons of junk "filter" applications. Without false positives, true positives, negative blaha.. bla... etc.

The above solution is THE ONLY way to get rid of SPAM. If you are not already doing it, DO IT NOW.

Re:Solution to SPAM is much simpler. (1)

Asztal_ (914605) | more than 7 years ago | (#17720030)

Dude... https://gmail.google.com/support/bin/answer.py?ans wer=12096 [google.com]

Also, random information: I have never given out my true address, just aliases, yet today, I received an unsolicited message about ViXXAGra and CiXXalis addressed to my true address! Well, I lie, it isn't really my true address, it's my address on the domain which I give out to websites (I use a different domain entirely for personal messages) -- but all the same, I might have to actually start receiving spam :(

Re:Solution to SPAM is much simpler. (1)

Asztal_ (914605) | more than 7 years ago | (#17720048)

Oh wait, actually, I suck, I did give it out. Haha. I administrate a phpBB forum. Apparently it shows emails in plain text and the current skin ignores the "Always show my e-mail address: Yes/No" option. Well, that sucks.

Fight Spam (1)

iminplaya (723125) | more than 7 years ago | (#17719994)

With Noemail.

This is crap (1)

feld (980784) | more than 7 years ago | (#17720038)

This article is complete shit. Anyone with half a brain knows how spammers work. And the #1 thing they try to do is send to your BACKUP if you have one.

"Why, oh why would they do such a thing?" you might ask.

Because if they send to your backup, there's a better chance that your backup server isn't setup as well as your main server. ie, you probably don't have a proper spam filtering service on there because you only use it in emergencies. This means their spam gets through your filters because it didn't go through any.

Huh, imagine that.
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