Getting mail out of the mailbox is trivial. Most reputable ISPs allow you to place custom filters on mailboxes. Others can, as was mentioned above, do cron jobs.
The trick is all in the format.
Email is a threaded medium. UBB is linear.
How does one reply to a topic?
How would quotes work?
How will we authenticate the user? Mail-from is useless, which leaves mailing the password each and every time.
The last time this was brought up, I said the same things.
If you want to try and do this, go ahead, but be aware that it will NOT be easy.
