[Dovecot] Errors in SASL authentication ("attempted master login")

[Grzegorz Staniak]

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>