We have an SMG on prem server set to manage 2 domains which have directory integration setup.
One domain is fully 365 and one is on Prem Exchange 2016.
Email from for spam notification is based on the domain name for O365.
All emails from our o365 to the other domain work.
Spam notifications do not get sent to the on prem exchange users, log shoes this error
[BrightmailScheduler_Worker-47] [SpamNotificationManager] ERROR - Cannot notify the user that he or she has new spam messages.
com.symantec.smg.controlcenter.BrightmailException: 451 4.4.62 Mail sent to the wrong Office 365 region. ATTR35. For more information please go to
ATTR35 response code when mail is sent to EOP/EXO - Exchange