Sendmail relay config

The joys of sendmail relay configuration!

To set up a sendmail relay, you need to configure your sendmail daemon to forward emails to a relay server, which will then forward them to their final destination. Here's a step-by-step guide to help you do so:

Step 1: Identify your relay server

You need to identify the IP address or hostname of the relay server. This can be a mail server provided by your internet service provider (ISP), a cloud-based email service, or a dedicated mail relay server.

Step 2: Edit your sendmail configuration file

The sendmail configuration file is usually located at /etc/sendmail.cf or /etc/mail/sendmail.cf. You can use a text editor to edit this file.

Step 3: Add the relay server to the sendmail configuration file

Add the following lines to the end of the configuration file:

# Relay server configuration
define(`RELAY_HOST', `your-relay-server-ip-or-hostname')
define(`RELAY_PORT', `25')  # or the port number used by your relay server

Replace your-relay-server-ip-or-hostname with the IP address or hostname of your relay server.

Step 4: Configure the sendmail relay

Add the following lines to the end of the configuration file:

# Relay configuration
FEATURE(`relayhost', `RELAY_HOST')
FEATURE(`relays', `RELAY_HOST')

This tells sendmail to use the relay server as the default relay host.

Step 5: Save and restart sendmail

Save the changes to the configuration file and restart the sendmail daemon:

sudo service sendmail restart

Step 6: Test your sendmail relay

Use the telnet command to test your sendmail relay:

telnet your-relay-server-ip-or-hostname 25

If everything is set up correctly, you should see a response from the relay server.

Additional tips and considerations

By following these steps, you should be able to set up a sendmail relay to forward your emails to a relay server.