a-HA! BIND address! I was looking for error address, notify address, etc etc.
not BIND address. I knew there was a little bit of magic I was completely
missing. Thanks a lot for that one!
So adding
main.cf
inet_interfaces = 2.2.2.2, 3.3.3.3
+ smtp_bind_address = 2.2.2.2
took care of that checking-RDNS-for-the-wrong-IP problem!
Once I also got my trasnport maps fixed mail received at the VPS IP address
gets forwarded correctly the office server.
Great! thanks!
Now to start testing all the failure modes and getting the inbound recipient
restrictions tweaked! Then the outbound SmartHost piece.