How to rewrite sender address in postfix using canonical_maps

To rewrite sender addresses in postfix using canonical_maps, you need to configure postfix to use a canonical map file.

Create the canonical map file:

First, create a file that will contain your canonical mapping. For example, let’s create a file named /etc/postfix/canonical.

# vi /etc/postfix/canonical

Add your address rewrites in the file. The format is:

original_address rewritten_address

For example:

olduser@example.com newuser@example.com

Postmap the canonical file:

After editing the file, you need to create a hash database file that postfix can use:

# postmap /etc/postfix/canonical

Edit your main postfix configuration file, main.cf, to specify the use of the canonical map. Add or modify the following lines:

# vi /etc/postfix/main.cf

Add these lines if they are not already present:

canonical_maps = hash:/etc/postfix/canonical
sender_canonical_maps = hash:/etc/postfix/canonical

Reload Postfix:

After making these changes, reload postfix to apply the new configuration:

# systemctl reload postfix

Verify the configuration:

Send a test email to ensure that the sender address is being rewritten as expected. Check the postfix logs for any errors or confirmation that the address has been rewritten.