I've looked and I've googled but cannot find a straight answer or HowTo! I can find plenty of options to create lists of known email addresses locally but this is not exactly what I want.
I am looking to be a relay host or secondary MX for a couple of my clients. I have my Postfix 2.5.5 mail server running the workaround.org ISP email setup http://workaround.org/ispmail/lenny on an Unbuntu Server, with the addition of Transport Maps suggestion found here http://workaround.org/ispmail-contributions I can happily receive emails for the domains that I host. I was happily holding emails in a relay queue over the weekend for a client whose power was off for the weekend, but with no address checking. Now what I would like to do is either be a relay host for a couple of other client or be the secondary MX. Here is my question, How can I modify my workarounds.org setup so I can verify and cache email addresses from the clients email server when visible? I want to cache them for the rare occasions when the clients email server is not accessible. I'd prefer not to have to manage lists of email addresses on my Postfix server but rather rely on the cached known email addresses. Any pointers would be greatly appreciated.
