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May 7 14:47:42 ttt dovecot: auth(default): worker-server(uid,yyy.yyy.yyy.yyy): Aborted: Lookup timed out May 7 14:47:42 ttt dovecot: auth-worker(default): mysql: Connected to lll.lll.lll.lll (imapauth)

"Lookup timed out" really shouldn't be happening.. That sounds like Dovecot's MySQL connections hangs after a while? You have some stateful firewall between Dovecot and MySQL that drops idling connections and afterwards starts dropping the connection's packets?

Indeed, there is a firewall with stateful inspection between Dovecot and MySQL.

Right, so the "Lookup timed out" works as intended. But I guess it should automatically retry when that happens. There would still be that 1 minute delay before that happens though.

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The only workaround is a downgrade to Dovecot 1.1.20.

Wonder what v1.1 does differently. I can't think of anything, really. The main fundamental problem is still that mysql connection hangs and the hang can't be detected/avoided. I think the right fix here would be to change your firewall settings..

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I think my problem has to do with the changes in src/auth/auth-worker-server.c in changeset 8859.

8559:b0bc4519332f?

Yep.