I'm a user of Gnus (why this is, would make a great post -- but I don't have time today). My organization allows me to use whatever e-mail client I want. This is a good thing. However, they coordinate their meetings using Outlook's calendar feature, which works over e-mail.
I poked around on the web for the best way to integrate Gnus in with these Calendar requests. I found a few packages out there that add the calendar requests to your emacs diary, which is neat -- but not quite what I was looking for. I wanted a way to respond to the meeting, not to mention, schedule my own meetings.
Last night, I finally came up with a simple way to accomplish this. I had our system adminstrator make me another POP3 account, besides my standard e-mail address the world mails me at. Say, ben-foo. Then, in my procmailrc on the mail server I added:
LOCKFILE=/home/ben/.procmail.lock
LOGFILE=/home/ben/.procmail.log
:0 Bc:cal
* ^BEGIN:VCALENDAR
! ben-foo@mycompany.com
The result, any email that comes in and looks like a calandar request, is routed to both my regular inbox and to my special pop3 account.
I then setup Outlook to poll the special account and not my regular e-mail account. It will only ever get e-mails for calendars, which is exactly the goal.
I also setup Outlook so that it had a from email address of my standard e-mail address, so any calendar invitations I send out, will have the right From address.
It's simple, but should be effective.
Kinda too bad for the rest of the people in my organization, as I now have the power to easily call meetings :-).