I've been forcibly logged out of SquirrelMail four times so far today, including once when I was sending an email. (When I logged back in, I received a message telling me that my send had been interrupted. So I clicked send again, only to find that it was now in my sent mail folder twice, making me look like a noob to a business associate.)
While today's experience has been particularly bad, I have been having similar problems for several months.
I've opened at least two support tickets on this, only to be told that no errors were found, or that they were doing maintenance (seriously, during the business hours, and without an outage notification?)
And while the dual send issue would seem to point to SquirrelMail being the problem, I was also told in all seriousness by a support tech that clearing my trash folder (at the time less than 200 messages, none of which were over 100K) might be the cause of the issues. Not very confidence inspiring.
I've been hosting at DH since December 2004, and I don't recall ever having problems like I've had within the last few months.
So is SquirrelMail that bad, or is it Dreamhost?