40MB!!!
In my last company, a multi-national project/consulting company with 14,000 users, we had an enforced allocation of 40MB per user. I had all sorts of un-necessary problems caused by this. The IT Director said that if the e-mail was important then it was to be "dragged to the appropriate project directory (yes, that's right; out of the mail system into the file system!!). I got around this organised a CD burner for each pc locally and trained the users on PST file management/backup.