16-767 means an invalid sending address (the one you are sending from, not that you are sending to)
The fact you are not using SMTP.office365.com:587 with StartTLS and instead using a relay and also not using authentication means one of 2 things is happening on this printer:
1. You have 2 emails as the from address
2. You have not set this device up on the relay server yet/properly
So for option 1, confirm you have it as Scan_Xerox@xxxxxx here too
For option 2 you need to do everything on the relay via option 3 of this link