How to setup cwp server to relay emails to remote mail server

Sending outgoing email through a 3rd party SMTP relay service is a quick and easy alternative to setting up a full fledged local email server.

Open /etc/postfix/main.cf and add the remote mail server hostname to end of the file:

relayhost = [remote.server.com]

If the remote system uses a different port number, please specify the port number:

relayhost = [remote.server.com]:587

In some situations, for redundancy, you may want to configure the relay via two or more remote SMTP server.In such instances, you may configure the following;

relayhost = [remote1.server.com]

fallback_relay = [remote2.server.com]

This gives us redundancy in a way so that if one of the SMTP relays is down, we can send emails out via the second one

Now, open /etc/postfix/mynetworks and the public IP of the remote mail server.For example,

192.168.6.45/32

192.168.7.34/32

This will let the mail server know exactly which networks are allowed to relay mail.This is a very important step

Restart postfix:

service restart postfix