Forum Discussion
Remote Server returned '550 5.7.501 Access denied, spam abuse detected.
Also found list of NDR Codes from O365
5.7.501 | Access denied, spam abuse detected | The sending account has been banned due to detected spam activity. | For details, see Fix email delivery issues for error code 451 5.7.500-699 (ASxxx) in Office 365. Verify that any account issues have been resolved, and reset its credentials. To restore this account’s ability to send mail, contact support through your regular channel. |
MicrosoftWhen sending from the onmicrosoft.com domain the cause of the NDR is most likely not that "The sending account has been banned due to detected spam activity."
As I said before, sending from the onmicrosoft.com domain is blocked when the originating IP is part of specific IP classes as a measure of preventing spammers to create free trial tenants and sending spam using them :)
