If I remember right R9 is when they added StartTLS support and let you put in the domain instead of an IP. If you are running an early R9.0 that does not support StartTLS you likely won't be able to get any provider to work without a relay server. If you can add the domain and StartTLS office365 should work (public IP needs whitelisted). Gmail works well, needs LessSecureApps enabled on the account, but from what I have heard gmail might be ending support for LessSecureApps.
The truth is just an excuse for lack of imagination.