i didn't know that, thanks for the correction

I currently support SquirrelMail for about 250 users. i wouldn't wish it on my worst enemy. worst webmail system EVER. i researched open source alternatives extensively in a effort to get off of it. basically it comes down to 2 if you want free/cheap. Zimbra or Atmail. Everything else price wise compares to google apps and exchange hosted prices. about 25-50 per user. Atmail is what i was leaning towards until i finally convinced them to buy exchange instead.

Note: for a modern GOOD webmail you need to have good administrative options, reliable dynamic interface, and syncing capability. (among other things) this means systems like HORDE etc are not webmail systems you can implement in the 21st century.

Zimbra is good and has a free edition(as well as a pay edition), but it is a yahoo company. Meaning updates are going to be iffy as they want you to use yahoo mail, not some open source off shoot they sponsored years ago.

Atmail does things like syncs to phones and has allot of administrative options. on top of that it is cheap and has support.

if i wasn't able to pull off a 11th hour exchange server i would have gone with atmail.