I use Qmail and need to set up an external SMTP relay server for outgoing mail, how can I perform this?
An external SMTP relay for Qmail can be set up in the $QMAIL_ROOT_D/control/smtproutes file. Add the relay server with the following command:
# echo ":RELAY_SERVER_NAME" > /var/qmail/control/smtproutes
(where RELAY_SERVER_NAME is the name of the SMTP relay server).
Then restart Qmail.