OK, here's the situation on which I'm currently working - I want to have multiple domains on my mail server (i.e. example1.com, example2.com, example3.org, example4.net, etc) which is easy.
I also want to be able to have the ability to have identical usernames across multiple domains, but have them refer to different accounts (i.e. email@example.com is a completely different mailbox than firstname.lastname@example.org), which is not too tough if you feel like remapping every user to a unique ID using virtusertable or other such schemes.
I also want to be able to allow users to check email via POP3, with the pop username using a format of email@example.com (i.e. the actual username used in the POP3 transaction might be firstname.lastname@example.org or email@example.com), which has got me scratching my head. I've seen software packages for other platforms that handle this well, but most of my google searches for linux mail software gets cluttered with sendmail references which fail to address this issue whatsoever.
Oh yeah, and I want to do it all on one IP (seriously).
Things that have occured to me (but which do not appeal, other than as a last resort):
1. recompile the pop3 daemon so it can figure out a mappings to a unique-id scheme (ala virtusertable)
2. read my O'Reilly sendmail tome 'till my eyes bleed to try and figure out a ruleset that will check local users before attempting to do an MX lookup/remote SMTP delivery (which would enable me to just create unix users called firstname.lastname@example.org, etc).
3. instead of recompiling pop3d, write a serious of scripts that would add links between unique mailboxes (ala virtusertable) and "fully qualified" references (i.e. email@example.com)
Of the above, I'm currently focusing on #2, and I suspect the winner(s) of pts here will probably provide that (if I don't get it first - in that case, the best suggestions get pts). If anyone needs any clarification on any of the above, please ask.
I'm really hoping someone has seen this before (it doesn't sound too, crazy, does it?) and can just post the appropriate ruleset (care to take it away, Jim?)