[Dovecot] help needed with dovecot authentication

[peter lawrie]

Hi
I have been asked to configure an dedicated rhel6 server for a customer.
I did not realise when I took this on how complicated it was going to be!
The purpose of the server is to host a group of websites for small
businesses.
It came with postfix-2.6.6-2.2  dovecot-2.0.9 and mysql-2.1.67-1
I have installed virtualmin 3.98, usermin1.540-1 and horde 5
About a dozen currently inactive websites have been set up, mail is in
/home/<domain>/Maildir
My problem is that I can telnet to postfix to send and receive emails and
can see these within postfix in webmin
I have been having many problems getting dovecot to connect successfully to
postfix.
I have also installed horde 5 which requires to authenticate to an imap
server - that is dovecot.
This one server is intended to provide all services, so plain
authentication is fine.
But I can't use /etc/passwd as the users are in virtualmin
I tried configuring ssl, with self-certification so the browser interface
is https:

At the moment I've restored dovecot.conf and conf.d/10-master.conf,
10-auth.conf and 10-mail.conf to their original settings.
So an attempt to login through usermin gives me this
Feb 28 19:44:19 scotz1 dovecot: auth: Debug: Loading modules from
directory: /usr/lib64/dovecot/auth
Feb 28 19:44:19 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libauthdb_ldap.so
Feb 28 19:44:19 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libdriver_mysql.so
Feb 28 19:44:19 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libdriver_sqlite.so
Feb 28 19:44:19 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libmech_gssapi.so
Feb 28 19:44:19 scotz1 dovecot: auth: Fatal: sql: Configuration file path
not given
Feb 28 19:44:19 scotz1 dovecot: master: Error: service(auth): command
startup failed, throttling

Previous to restoring the conf files I  was getting this from horde
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Loading modules from
directory: /usr/lib64/dovecot/auth
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libauthdb_ldap.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libdriver_mysql.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libdriver_sqlite.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libmech_gssapi.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: auth client connected
(pid=25627)
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: client in:
AUTH#0111#011PLAIN#011service=imap#011secured#011lip=127.0.0.1#011rip=127.0.0.1#011lport=143#011rport=439
54#011resp=dGVzdHNjb3R6LmNvLnVrAHRlc3RzY290ei5jby51awBwYXNzd29yZA==
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Loading modules from
directory: /usr/lib64/dovecot/auth
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libauthdb_ldap.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libdriver_mysql.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libdriver_sqlite.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: Module loaded:
/usr/lib64/dovecot/auth/libmech_gssapi.so
Feb 28 17:55:02 scotz1 dovecot: auth: Debug: passwd(testscotz.co.uk,127.0.0.1):
lookup
Feb 28 17:55:02 scotz1 dovecot: auth: passwd(testscotz.co.uk,127.0.0.1):
unknown user

Horde is using mysql for its database, but I don't particularly care what
dovecot uses, although it seems sensible to do the same
I have created and removed several mysql databases during my attempts to
get this to work.

I would greatly appreciate some assistance with this as every 'howto' I
have found by googling describes different setups and just gets me deeper
in the mire!

I want an authentication mechanism on this one server that virtualmin users
and horde users (same people!) can use for imap mail.

I thought I knew what I was doing before I took this one on (I have
configured and manage a dozen centos servers), but this one is making my
head spin.
Yours in hope!
Peter Lawrie