dovecot - Aug 2013 - Errors in SASL authentication ("attempted master login")

Hi,

I'm using dovecot 2.2.4 (with Postfix 2.8.4) as both the SASL
authentication backend and the delivery agent, and I keep getting
lines like the following in the dovecot.log from the authentication
subsystem:

auth: passdb(toshiba1 at domain,8.8.8.8,master): Attempted master login
with no master passdbs (trying to log in as user: plain)

The connections come from an old (embedded) mail client in a
printer-fax machine. I googled for this specific error, but I only
found info about old clients using "user\0user\0pass" string
incorrectly during authentication, which caused a problem for earlier,
development versions of dovecot. Actually, I recently migrated from
1.2 to 2.2.4 exactly to alleviate this situation, but the errors
persist. Is there a way to remove the problem or work around it?

Regards,
GS
-- 
Grzegorz Staniak <gstaniak [at] gmail _dot_ com>

On 8.8.2013, at 12.58, Grzegorz Staniak <gstaniak at gmail.com> wrote:
> I'm using dovecot 2.2.4 (with Postfix 2.8.4) as both the SASL
> authentication backend and the delivery agent, and I keep getting
> lines like the following in the dovecot.log from the authentication
> subsystem:
> 
> auth: passdb(toshiba1 at domain,8.8.8.8,master): Attempted master login
> with no master passdbs (trying to log in as user: plain)
> 
> The connections come from an old (embedded) mail client in a
> printer-fax machine. I googled for this specific error, but I only
> found info about old clients using "user\0user\0pass" string
> incorrectly during authentication, which caused a problem for earlier,
> development versions of dovecot. Actually, I recently migrated from
> 1.2 to 2.2.4 exactly to alleviate this situation, but the errors
> persist. Is there a way to remove the problem or work around it?
So in general authentication works, but not from this client? Sounds like the
client is using a broken SASL authentication. Nothing you can really do about
it. Note that the above Dovecot message is an "info" message, not an
error message.