Postfix relay all mail

A classic configuration!

To configure Postfix to relay all mail, you'll need to modify the main.cf file, which is the main configuration file for Postfix. Here are the steps:

Step 1: Edit the main.cf file

Open the main.cf file in a text editor, usually located at /etc/postfix/main.cf (on Linux systems).

Step 2: Set the relayhost parameter

Add the following line to the file:

relayhost = <your-relay-host>

Replace <your-relay-host> with the hostname or IP address of the mail relay server you want to use. For example:

relayhost = [mail.example.com]:25

This sets the relay host to mail.example.com on port 25.

Step 3: Set the mydestination parameter

Add the following line to the file:

mydestination = $myhostname

This sets the local hostname as the destination for mail.

Step 4: Set the mynetworks parameter

Add the following line to the file:

mynetworks = 127.0.0.0/8 [::1]/128

This sets the local network (127.0.0.0/8) and the loopback interface ([::1]/128) as the only networks that can send mail directly to the Postfix server.

Step 5: Restart Postfix

Restart the Postfix service to apply the changes:

sudo service postfix restart

Verify the configuration

You can verify the configuration by running the following command:

postconf -n

This will display the current configuration settings, including the relay host.

Test the configuration

Send a test email to a recipient outside your local network to verify that the mail is being relayed correctly. You can use a tool like telnet to test the connection:

telnet <your-relay-host> 25

Replace <your-relay-host> with the hostname or IP address of the relay host. If the connection is successful, you should see a response from the relay host.

That's it! With these steps, you should now have Postfix configured to relay all mail to the specified relay host.