We currently have an SFB 2015 Enterprise setup which includes an Edge server. I was not a part of this initial setup but have been recently assigned to manage our SFB environment.
Currently, we have several domains federated to allow external messaging to these portions of our organization. When adding federated domain contacts, I'm able to see them as well as their status however when we send messages, they are never received. There are no error messages, nothing telling me where to look or what may be wrong.
My initial thought is that this could be because while the SMTP and SIP addresses match, the UPN does not. Is that a possibility? What else do you think this could be? Thank you in advance.
It is not that the UPN/Email doesn't match the SIP address since you are able to find the federated contact (you can see their presence). I rather think that it is a problem with certificate (their Edge doesn't trust your Edge), firewall issues (ports not opened) or some other configuration problem.
I suggest that you use the Skype for Business Debugging tool and collect logs to analyze.