Email relay via 365 blocks spoofing of user name

configuring the email relay for user password reset:

for use via 365

the relay gateway is “

setting user & password works.

But 365 WILL NOT allow spoofing of user details.[]:25, delay=1.3, delays=0.01/0/0.92/0.38, dsn=5.2.252, status=bounced (host[] said: 554 5.2.252 SendAsDenied; not allowed to send as;

it needs some way of ensuring all teh details match, for it to pass the relay requirements of 365


seems setting this system variable to match the email login fixes it…: