While asking my mail server users to set up their Google Apps mail pending transition, one of them flagged up a bug in POP he’d found. So I went off to research it and came across a few issues with POP and then with IMAP.
Turns out that Gmail doesn’t properly conform to the RFCs for POP or IMAP. For POP, the leave/delete mail on server is broke, athough partially fixed by adding a “recent” tag to the setup. It also appears that IMAP is broke – all to do with the fact that Gmail uses labels to mimic folders and these folders aren’t the IMAP ones.
Discussed more at the Sort of “Leave on server” facility on Gmail’s POP feature and Google Forums
So given that my users are all POP people and I’m a POP/IMAP person with keen interest in e-mail on phones/PDAs these are pretty much deal breakers – sorry Google.
I’ve looked a little bit at the Microsoft alternative, but it’s MS focused and I’ve got linux/mac fans as users. Also the MS live mail’s in your face advertising is just too much.