I administer a handful of shared web hosting servers. Recently, Yahoo has been deprioritizing/greylising all email sent from these servers. I am getting the dereaded 421 4.7.0 [TS02] Messages from my.ip.address temporarily deferred message from Yahoo and their postmaster has been unresponsive.

I am unable to find any way to set up a feedback loop like AOL has for my IP address -- I did find a way to set up a feedback loop for a given domain, but we host hundreds of domains, and don't have the time to set up that many feedback loops. So what I'd like to do is twofold:

1. Configure Exim to send all email destined to an @yahoo.com address to a relay, a new server which has an IP that yahoo is not blocking.
2. Configure Exim (or maybe the relay) to log all emails sent to @yahoo.com, so I can review them and, in case one of my uses is violating ToS and sending SPAM to yahoo users, take the appropriate action.

How could I accomplish these? Or, does anyone have any other advice for how to get mail to flow through Yahoo and ensure that any email generating complaints is brought to my attention? (For what it's worth, these servers are not listed on any major blacklists)