[Dovecot] Dovecot / Exim with Multiple Domiains

[Marc Perkel]

I'm using a very old scheme for doing multiple domains using an old 
Linuxconf based setup. Each domain has it's own passwd/shadow file. It 
works but I need something new and modern and has a web interface and 
perhaps a mysql backend or something else good.

So - what are people using out there for managing email users and domains?
Thanks in advance.