Postfix to use a third party SMTP server

This instructs postfix to use a third party SMTP server. It’s useful when you want to relay e-mail from an internal server which uses a dynamic IP address.

Ensure postfix is installed, and let’s have all e-mail sent to root relay to an external e-mail address:

nano /etc/postfix/sender_canonical
root     youremail@provider.tld
Postfix requires the modifications to be hashed:
postmap hash:/etc/postfix/sender_canonical
postconf -e "sender_canonical_maps=hash:/etc/postfix/sender_canonical"
Now let’s instruct postfix to use third party SMTP to route e-mail:
nano /etc/postfix/main.cf
relayhost = yoursmtp.provider.tld
service postfix restart
Finally update system aliases:
nano /etc/aliases
root:   email@domain.tld
newaliases