[Dovecot] auth-worker temporary failures causing lmtp 500 rejection

[Timo Sirainen]

On 26.1.2012, at 12.14, Mark Zealey wrote:

> I'm using dovecot 2.0.16 with a mysql user database. From time to time when we have a big influx of messages (perhaps more than 30 concurrent rcpt to:<> sessions at the same time so no auth-workers free?) or when we have a transient issue connecting to the database server, we see the message:
> 
> Jan 25 16:38:23 mailbox dovecot: auth-worker: sql(foo at bar.com,1.2.3.4): Unknown user

This happens only when the SQL query doesn't return any rows, but does return success.

> and the lmtp process returns:
> 
> 550 5.1.1 <foo at bar.com> User doesn't exist: foo at bar.com
> 
> This would be correct for a permanent error where the user doesn't exist in our database, however it seems to be doing this on transient errors too. Is this an issue with the code or perhaps some setting I have missed?

The problem is that temporary errors are returning "unknown user". Can you reproduce this somehow? Like if you stop MySQL it always returns that "Unknown user"?