SymptomsSymptoms from KB article Drweb rejects email with error "dwlib: fd: recv(4) failed - Connection reset by peer" are reproduced after a Parallels Plesk Panel upgrade.
CauseMaxChildren option in drweb32.ini is always rewritten with value 4 when there is an install/upgrade of package psa-drweb-configurator.
Before an upgrade, make a copy of /etc/drweb/drweb32.ini file:
# cp /etc/drweb/drweb32.ini /etc/drweb/drweb32.ini.copy
After an upgrade, replace MaxChildren value of /etc/drweb/drweb32.ini by value from a copy made before upgrade.