When we try to send an email via webmail get this error
sendmail unknown error 111
While we check the mail log '/usr/local/psa/var/log/mailllog' file you can find this message:
qmail-queue-handlers[11558]: Unable to get information about group 'popuser': Permission denied
This error is due to invalid permission in the /etc/groups. change the permission on groups file.
# chmod 644 /etc/groups