Has anyone created a simple POP3 and SMTP server using TWISTED?

[Zoo Keeper]

Or by any other means for that matter.

I have two domains, one for me, one for my wife, for our web sites.  I
want our own mail servers because our ISP has changed names 3 times in 4
years.  Right now I am using a great product (my server is BeOS, btw)
but it is a trial version and the minimal license is for 50 users and
costs too much.  So, I figured I'd write one in Python, but I wanted to
check here first to make sure it hasn't already been done so that I am
not wasting time researching and writing something that already
exists...

Thanks!

Mike