Quoting Jukka Salmi (jukka-netbsd@2003.salmi.ch):
> I want to set up a mail server providing SMTP and IMAP services.
> Furthermore I'd like to manage domains and users virtually. I've
> done this before using Linux, qmail, Courier IMAP and maildrop
> (Courier IMAP and maildrop using virtual users defined in a userdb),
> but now I want to use NetBSD and Postfix.
>
> Which authentication systems exist / are recommendable on a NetBSD
> system? It's possible to keep maildrop, Courier IMAP and the userdb,
> but I'd like to get to know some other solutions for managing virtual
> users.

Me?  I like LDAP.  Useful for so many things.
Works fine with sendmail and cyrus and squirrelmail
and the imitators of each.