[Dovecot] LMTP proxy too many DATA output timeout (perhaps)

[Luca Palazzo]

Hi All,
we are getting a lot of this message from dovecot director. They seem to 
be too many.
Backend servers do not log anything and postfix logs a lot of these errors.
It seems that dovecot strategy handgling data output timeout when 
proxying LMTP is or too aggressive or may have some other problem.

This error generate sometime a lot of dupicate deliveries, probably 
because meanwhile real server has finished delivering the mail, proxy 
drops the connection.

Another symptom, maybe related to duplicate uid patch, is that we are 
receiving blank email.

What may I look further?

Regards
Luca