OneC0de writes "I have been the IT admin for a small/medium business for the last 3+ years. Currently our email system is a IMAP/POP/SMTP setup hosted through another company across the country. We've continually had email problems ranging from dropped connections, and missed messages, to our host forcing our users to a 500MB inbox which we regularly have to flush. We have Small Business Server 2008 in-house running our active directory/group policy. I have normally setup Exchange on SBS for most of my clients but this business in particular is pretty against Exchange (being a Windows product). The owners are ready to upgrade their email system, but are not sold on going to Exchange. Many users at this company are on Thunderbird and don't want to make the switch to Outlook. The owners have asked me to find other email server solutions. One thing their "Linux friend" suggested was iRedMail. They definitely want to host it in-house to save on cost and increase connectivity while at the main office where most emails are done. Many users in the office have 2GB — 10GB of emails stored from the last 7+ years, just on their local machines (not being backed up regularly). Right now there is no shared calendars, or global contact list but they don't see that as a much needed feature anyways. We also use SquirrelMail 1.49 for web access, but it seems old and outdated.
So I guess my question is, are there open-source, or cheap mail servers you would recommend? Is there a good argument for Exchange other than (it's free and sitting in your server room right now, just need to "turn it on")? Would you recommend Exchange or go against it? One of the things the owners would like is anti-spam, anti-virus, and maybe some kind of archiving capabilities. Many users in the office also have mobile phones and would like access to the emails while on the go. Suggestions, comments, complaints, free beer?"