That's interesting. I'm using uwimap and popa3 under OpenBSD, and they both coexist quite nicely. I use SquirrelMail to do my webmail.
The reason for both is pretty simple - I prefer POP3 for use with a mail client - I like to be able to combine multiple email accounts into one overall view, which Outlook Express lets me do pretty simply. I've got five different email accounts that I check/dump into OE via POP3, and they can all get processed into the same folders with the same filters.
It might be possible to do what I want via IMAP, but I couldn't be bothered
The IMAP is just so that I can use squirrel mail - which is for security, when you get right down to it. I've got my squirrel mail set up as an SSL site, so that passwords aren't sent in plain text. I could have accomplished the same thing by tunnelling POP over SSH, but it's far more complicated than I wanted to get.
I don't do any IMAP filtering though, so everything is still in my "INBOX" on the web mail - I check my mail throughout the day at work, deleting the ones that I don't care to keep. Every now and then, I fire up Outlook Express, and download the ones I want to keep (as well as checking all my other email accounts, which aren't used nearly so much)
As far as I was aware, IMAP and POP3 are only interfaces to get at the underlying mail system, so unless IMP does some stuff with mail as it's received, it should still be available via POP3.
EMail is far too complex under the hood - especially for how insecure it is. (JMHO)
How's that novel for you?