In this post, let’s have a look at the error message “5.7.64 – TenantAttribution; Relay Access Denied” that you get when working with Microsoft 365 Exchange Online.
These are the errors that you usually receive when there is a problem in delivering the email message that was sent by you. These errors are generated and sent by Office 365. This is usually alled as DSN which stands for delivery status notification or in simple words bounce messages.
NDR or Non-delivery report is one of the common type of message that you receive which indicates to the user that the email was not delivered.
5.7.64 – TenantAttribution; Relay Access Denied
You use an inbound connector to receive messages from your on-premises email environment, and something has changed in your on-premises environment that makes the inbound connector’s configuration incorrect.
For more information, see Fix email delivery issues for error code 5.7.64 in Exchange Online.