Nowadays, quite a few ISPs block port# 25 which is the default SMTP port for relaying email for security purposes, so you need to configure an alternative port for SMTP connection.
Use instructions below to configure an additional alternate SMTP port in a Plesk Server running in Redhat Enterprise Linux Version 4/5 or CentOS version 5 in Qmail Server.
Choose any unused port and add it to the /etc/services file, for example:
smtp_alt 8425/tcp mail # Alternate SMTP Port
smtp_alt 8425/udp mail # Alternate SMTP Port (optional)
Make a copy of /etc/xinetd.d/smtp_psa to /etc/xinetd.d/smtp_psa_alt and correct service line within new file:
service smtp_alt
Below is a sample of smtp_psa_alt file.
service smtp_alt
{
socket_type = stream
protocol = tcp
wait = no
disable = no
user = root
instances = UNLIMITED
server = /var/qmail/bin/tcp-env
server_args = -Rt0 /var/qmail/bin/relaylock /var/qmail/bin/qmail-smtpd /var/qmail/bin/smtp_auth /var/qmail/bin/true /var
/qmail/bin/cmd5checkpw /var/qmail/bin/true
}
Restart xinetd and Qmail
service xinetd restart
service qmail restart
SMTP connections will be accepted on the both standard and 8025 ports. You may also need to reconfigure Horde IMP (webmail) settings so it uses the alternative SMTP port too. This can be done editing the following file in Horde webmail:
/etc/psa-horde/imp/servers.php file under smtpport parameter for both IMAP and POP3 servers.
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