[avar]

This may not be what you're asking, but it's rather trivial if you're setting up an SMTP gateway that proxies traffic to another SMTP that handles the IP address reputation management etc.

E.g. I do that with Exim on my Debian laptop and have it relay outgoing messages to Gmail's SMTP. It's great if what you want out of it is being able to send E-Mail while "offline", the messages will get locally queued until you've got an outgoing connection, much better than relying on individual MUA's to handle that, and it'll work with one-off invocations like piping to mail(1) etc.