Postfix SMTP Relay for RunCloud-Managed Servers

When a RunCloud-managed server (like wphost02) accumulates stuck email in Postfix's queue because port 25 outgoing is blocked, the fix is to relay through a working SMTP server. This is common with netcup infrastructure where only port 2525 works.

Symptoms

mailq shows 50+ stuck messages with "Connection timed out" to port 25 destinations
Postfix logs show: connect to <mx>[...]:25: Connection timed out
WP Mail SMTP on WordPress may work (if configured for port 2525), but the system's PHP mail() function goes through Postfix which tries port 25

Diagnosis

mailq                          # Count stuck messages
grep "status=deferred" /var/log/mail.log | tail -5   # See delivery failures

Fix: Relay through MXroute port 2525

Configure Postfix as a satellite relay through mail.germainebrown.com:2525 with SASL auth:

postconf -e "relayhost = mail.germainebrown.com:2525"
postconf -e "smtp_sasl_auth_enable = yes"
postconf -e "smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd"
postconf -e "smtp_sasl_security_options = noanonymous"
postconf -e "smtp_tls_security_level = encrypt"
postconf -e "smtp_tls_wrappermode = no"

Create the SASL password file:

echo "mail.germainebrown.com:2525 shonuff@germainebrown.com:Catches.bullets1985" > /etc/postfix/sasl_passwd
chmod 600 /etc/postfix/sasl_passwd
postmap /etc/postfix/sasl_passwd

DNS: The sender domain must resolve. The system hostname (wphost02) will be the default sender domain, which MXroute rejects. Fix by setting a valid myorigin and generic address mapping:

postconf -e "smtp_generic_maps = hash:/etc/postfix/generic"
postconf -e "myorigin = /etc/mailname"
echo "apextrackexperience.com" > /etc/mailname
echo "@wphost02 contact@apextrackexperience.com" > /etc/postfix/generic
echo "root@wphost02 contact@apextrackexperience.com" >> /etc/postfix/generic
postmap /etc/postfix/generic

Restart and flush:

systemctl restart postfix
postqueue -f

Verify

mailq                          # Should show: "Mail queue is empty"
grep "relay=mail.germainebrown.com" /var/log/mail.log | tail -5  # Check deliveries

Note on stuck emails

Emails queued BEFORE the relay was configured will likely hit their 5-day expiry and bounce locally. The fix ensures new emails deliver correctly. Old ones may need to be re-sent by the application (WPForms, etc.).

Diagnostic: Stuck Postfix after RunCloud reboot

When wphost02 reboots, Postfix may start stuck in an earlier state. Check systemctl status postfix for unexpected stop times or stale PIDs. A systemctl restart postfix followed by postqueue -f is usually sufficient to clear any accumulated queue.

Credentials used

Relay host: mail.germainebrown.com:2525
Auth user: shonuff@germainebrown.com
Auth pass: Catches.bullets1985 (stored in send-shonuff.py and sasl_passwd)
Sender override: @wphost02 → contact@apextrackexperience.com

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