Resolution
For Linux users.
Log in to the Parallels Plesk Panel (PP) server and try "telnet localhost 25." If SMTP works and Qmail is used as a mail server, the output should be:
# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 hostname.tld ESMTPor in case Postfix is used (available since PP v. 9):
# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 hostname.tld ESMTP PostfixIf you run "telnet localhost 25" on the Plesk server and see another greeting, check article 1374.
Make sure that the 'tcp-env' server with appropriate arguments is used in xinetd/inetd configuration for SMTP service.
If you run "telnet localhost 25" on the Plesk server and see something like:
telnet localhost 25
Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Connection refused
telnet: Unable to connect to remote host: Connection refusedCheck if xinetd is running:
ps ax | grep xinetd
2155 ? Ss 0:00 xinetd -stayalive -pidfile /var/run/xinetd.pidIf not, try to start it "/etc/init.d/xinetd start". Otherwise, make sure that /etc/xinetd.d/smtp_psa and /etc/xinetd.d/smtps_psa files are OK. Compare them with ones from some working server.
Check /var/log/message for possible errors during the restarting of the xinetd service. Fix the problem and restart xinetd "/etc/init.d/xinetd restart".
If you see an error in 'messages' like:
smtp/tcp server failing (looping), service terminated
see article 1470.
For FreeBSD users.
On Plesk for FreeBSD, SMTP is run using 'inetd' super-server. You should check that the 'inetd' process is running and that the /etc/inetd.conf contains records for Plesk SMTP service.