[Dovecot] SASL auth and proxy

[Timo Sirainen]

On Wed, 2010-09-29 at 17:07 +0200, mailing at securitylabs.it wrote:

> Hello, I'm finding a way to have a pool of smtp-auth servers in front 
> of my actuals servers to permit relay to our customers. Now users sends 
> emails connecting to the right IP via mail.domain.tld, with 
> authentication. Every server has it's own user database in mysql.
> 
> Can I use:
> 
> http://wiki.dovecot.org/Authentication/MultipleDatabases
> 
> to tell Dovecot to authenticate with every MySQL database on the servers 
> "behind"?

Yes, but if you have many of them, that's quite a lot of unnecessary SQL
lookups. And since they're done one at a time each lookup slows down the
authentication.

> If yes, is there a better way to do this considering I'm already using 
> some proxy machines (dovecot) for pop3/imap and so I already have a db 
> with domain.tld -> IP of the server? I also have some machine without a 
> MySQL DB for users (vpopmail + cdb), so the option with 
> MultipleDatabases will be good only for some machines.

You could always use checkpassword script as passdb to implement
whatever kind of logic you want.