The below is specific to CentOS-5.4 and may work similarly with other distros.
- Additional packages required if not installed already:
sendmail-cf
m4
make
cyrus-sasl-plain - Edit ”/etc/mail/sendmail.mc”:
define(`SMART_HOST', `{smtprelay.domain.tld}')dnl
FEATURE(`authinfo',`hash -o /etc/mail/authinfo.db')dnl - Create file ”/etc/mail/authinfo” with below contents and chmod 640:
AuthInfo:smtprelay.domain.tld "U:{username}" "P:{password}" "M:PLAIN"
- Update the sendmail conf and db hashes:
cd /etc/mail
make - Restart sendmail for the new configs to pick up.
- Now mails sent to localhost is relayed via your SMTP provider.