Relay postfix email specific from address

To configure Postfix to relay emails from a specific email address, you can set up a sender-dependent transport map. This allows you to specify different relay hosts or transport methods based on the sender’s email address. Here’s how to do it:

1. Edit the main.cf File:

   Open the Postfix configuration file /etc/postfix/main.cf in a text editor with superuser privileges:

   sudo nano /etc/postfix/main.cf
   

2. Configure sender_dependent_relayhost_maps:

   Add or modify the sender_dependent_relayhost_maps parameter in your main.cf file to specify the mapping of sender email addresses to relay hosts. This parameter should point to a file that contains these mappings.

   sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay
   

3. Create or Edit the Sender Relay Map File:

   Create or edit the /etc/postfix/sender_relay file to specify the sender-dependent relay hosts. Each line in this file should be in the format:

   sender@example.com   smtp:[relayhost.example.com]:587
   

   Replace sender@example.com with the sender’s email address, and smtp:[relayhost.example.com]:587 with the relay host configuration. You may use square brackets [] if you need to specify a specific port number. Ensure you have square brackets around the relay host for consistency.

   For example, to relay emails from sender@example.com through relayhost.example.com on port 587:

   sender@example.com   smtp:[relayhost.example.com]:587
   

4. Generate the Sender Relay Map Database:

   After adding your sender-dependent relay rules, generate the database file:

   sudo postmap /etc/postfix/sender_relay
   

5. Restart Postfix:

   To apply the changes, restart the Postfix service:

   sudo systemctl restart postfix
   

Now, emails sent from the specified sender (sender@example.com in this example) will be relayed through the designated relay host (relayhost.example.com in this example) as per your configuration.

Make sure that you have the necessary permissions and access to modify Postfix configuration files. Additionally, consider security and authentication requirements for your relay host, as relaying email often requires proper authentication.