Symptoms
Duplicate messages are received by qmail users. The following errors can be found in the maillog:
root@server log]# less -i maillog.1 | grep "_but_connection_died"
Connected_to_<IP_address_1>_but_connection_died._Possible_duplicate!_timed_out_(#4.4.2)/
Nov 26 17:50:53 pemlinmail01 splogger: 1385484653.371186 delivery 208765: deferral: Connected_to_<IP_address_2>_but_connection_died._(#4.4.2)/
Nov 26 18:09:06 pemlinmail01 splogger: 1385485746.461143 delivery 209075: deferral: Connected_to_<IP_address_3>_but_connection_died._Possible_duplicate!_timed_out_(#4.4.2)/
Nov 26 18:11:33 pemlinmail01 splogger: 1385485893.930699 delivery 209114: deferral: Connected_to_<IP_address_4>_but_connection_died._(#4.4.2)/
Cause
Qmail cannot connect to remote host during the time specified in the /usr/local/qmail/shared/control/timeoutremote file.
Resolution
Increase timeout using command as below:
# echo 180 > /usr/local/qmail/shared/control/timeoutremote