I'd be concerned about using DreamHost for business/mission critical email.
PROS: Cheap price, IMAP, webmail (Squirrel Mail), generous storage for the cheap price.
CONS: Increased downtime compared to others. Never LOST any mail that I'm aware of, but network connectivity/file server issues have had email client access down for hours at a time, every other month or so, which can really bite it when folks are working to deadline...
I think (hope) that some of the stability issues they've had over the past year are getting better. I can certainly say that the response time and effectiveness of tech support have improved during the latter part of the year.
But their service level isn't up to an A-line ISP (but they are a LOT cheaper, so...)