So if you’re looking for an easy way to relay outgoing emails based on sender address, give sender_dependent_default_transport_maps a try! To verify the above settings, I have sent an email from the terminal using [email protected] email address. As per the above configuration, the emails from @example.net should relay through 192.168.1.10:25 SMTP server. As per the logs, the email was relayed through the correct SMTP server. For those who need to relay outgoing emails based on the sender address, the sender_dependent_default_transport_maps parameter in Postfix can come in handy. This parameter enables you to specify which transport a message should be routed through based on its sender address.
