Drowning in a sea of exchange data...
SMTP is enabled for the account
From within exchange,
We have a client frontend transport using TLS, Basic Auth only after starting TLS + Integrated Windows auth
Permission groups set to exchange users only
The default frontend transport uses TLS + Mutual Auth TLS, Basic Auth only after starting TLS + Integrated Windows auth, Exchange Server auth
Permission groups set to Exchange servers Legacy Exchange Servers and anonymous
The outbound proxy transport uses same settings as default frontend except permission groups set to exchange servers only
Let me know what other info you need if that's not what you're looking for