Darren Smith writes:
We have been told that "warming up" the IP is the way to go - that is, cutting over just some of the traffic a little at a time.
AIUI the IP that receiving ADs care about is the last hop IP, ie, the source of the SMTP connection. I haven't done this myself, so take this with a grain of salt, but I would
(1) Document the new IP with an MX record for your domain, as well as A and AAAA records as appropriate. This means you'll have to configure it to MX for the whole domain, of course. You can keep the load down by giving it low priority.
(2) Set up the MTA on the Mailman host to send occasional mail via the new host. If the MTA doesn't know how to do it itself, you could do something really hacky like restart the Mailman host's MTA with different configurations at say 8am (current outgoing MX) and 5pm (new outgoing MX).
You could also do something even more hacky with the routing tables.
I don't think this really has anything to do with Mailman itself, although it probably wouldn't be hard to add code to round-robin some outgoing mail to an MTA configured to MX via the new IP.
So what I am looking for is a way for all mail on our domain to be sent to our current mailman installation,
All mail, or just the list mail?
and based on some configuration (certain mailing lists?)
I would not do this by mailing list. Some reputation systems work on tuples, ie, (target mailbox, source IP, source domain), so only the lists configured to go via new IP would "warmed up". It also seems likely that recipient domains with only a few subscribers on your lists would have unbalanced distribution across your lists, and so might be missed entirely.
certain emails being sent out to the list subscribers will first be forwarded to the new server and be sent from the new IP address.
Does that make sense?
As a strategy, yes, but how difficult to implement reliably, I don't know.
Does anyone know a way that mailman/postfix can be configured to accomplish this?
Is there a different forum where I might be able to ask experts about this?
My feeling is that you want to ask on Postfix channels, since I don't see a good reason to involve Mailman itself in what is really a task for the MTA. Mailman was deliberately designed to not know anything about outgoing mail except a host and port to send to.