How can I configure Postfix to send via IP based on origin domain?

Question

I have a server that hosts multiple websites that send email. Each domain has its own IP address, and I would like Postfix to send outgoing email on the same IP so the reverse DNS points back to the same domain, but Postfix always sends via the first IP it binds to. I would like to configure Postfix to via different IP based on the domain of the sender's email address.

Answer 1

You could use sender_dependent_default_transport_maps to select different transports according to sender. Each transport could use smtp_bind_address to bind to different IPs.