http://intrcxv4fa72e5ovler5dpfwsiyuo34tkcwfy5snzstxkhec75okowqd.onion/blog/email-service
As for multi user set-ups, I followed the MySQL route, for which I loosely followed this guy's write-up .
This also allowed me to create a registration form. The two backend programs I use are Dovecot (with Sieve and SpamAssassin) and Postfix. Daring, aren't we? Dovecot was by far the most annoying to configure, and the best advice I can give is to read through all the config files and to adjust as you see fit.