With a PBXact UC 40, I have tried and tried to set up email using my O365 account to no avail. Oddly, I can get GMail to work though gmail is a personal account vs business.
Now would doing this affect any possible support contract you have with Sangoma for your PBXact UC 40, I do not know…
I do not believe it is possible to get things working without those address remaps as I believe not all sender email address are legit even when “My Domain” (Postfix’s mydomain) is set correctly.
(One of these days I will try to confirm this…)
There’s a pretty big thread about someone who finally got it working in the end here:
By the way, as I said somewhere in there, resist the temptation to set My hostname (Postfix’s myhostname) and My domain (Postfix’s mydomain) to the same thing, it will cause problems the way the mail server software (Postfix) is setup by default…