How to set up Postfix for use with Freerelay

Put your generated key in /etc/postfix/certs/freerelay-key.pem, and the certificate you received by email in /etc/postfix/certs/freerelay-cert.pem.

Then, edit /etc/postfix/ and add the following lines:

smtp_use_tls = yes
smtp_tls_key_file = /etc/postfix/certs/freerelay-key.pem
smtp_tls_cert_file = /etc/postfix/certs/freerelay-cert.pem
relayhost = []:2525

After doing that, restart postfix and check that relaying works. Freerelay listens to port 25, 587 (submission), 6667 (irc) and 2525, so if any of those are blocked in your network, try another one.