[Dovecot] Problems with authentication

[Lapo Luchini]

Hi there.
I've got a running qmail+vpopmail+mysql5 server on FreeBSD and I would like to
give IMAP access to it (both for user's sake and to have a decent webmail), so I
decided to install dovecot (it certainly does its work on my home box).
Problem is: I haven't had success with authentication.

At first I tried the most obvious: using the vpopmail backend.
Unfortunately I received lots of "vmysql:  MySQL server has gone away" just like
in http://article.gmane.org/gmane.mail.imap.dovecot/10321

So I decided to spice up a query to vpopmail's MySQL table, and there another
problem was waiting for me: "Access denied" just like in this thread
http://article.gmane.org/gmane.mail.imap.dovecot/9077
Only difference: in my case using OLD_PASSWORD() didn't solve the problem and
-thinking about it better- couln't possibly have solved it: that FreeBSD is a
recent fresh install and I installed MySQL 5.0.18 from sources using the "ports"
system, so a library with no support for new PASSWORD() has never seen the light
on that box.

I kinda went around the problem using a shell script to dump the MySQL table to
a SQLite file and authentication dovecot against that, but while this
work-around can do for a little bit I'd really like to solve the problem itself,
and avoid having to keep ni sync those two DBs (no, unfortunately vpopmail
doesn't support SQLite, else I'd use that: it would also have the nice
side-effect that a "down" on mysql side wouldn't hurt the mail subsystem).

Any suggestions or idea how I could solve or, at least, better diagnose the
problem(s)?

Yours,
  Lapo