[Exim] Best IMAP and POP Servers?

Of course the word "best" means different things to different people.
I'm using something that works but isn't well supported and wondering
what else is out there. Here's my situation.

I'm using Washington Universities IMAP with the Virtual IMAP patch. This
allows me to run multiple domains on a single IP address. I'm running
about 50 virtual servers now. To make this work the entire email address
is used for the login name - and there are multiple passwd/shadow files
in the /etc/vhome directory. It is compatible with Linuxconf for
management. The problem is that there's just one guy who supports the
virtual patch and he doesn't update things very often.

So - is there any other solutions out there that do something like this?
I need virtual domains. I need to run it off 1 ip address. What are
other people doing for multiple domains?