In this post, let’s have a look at the error message “5.7.511 – Access denied, banned sender” 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.
5.7.511 – Access denied, banned sender
The IP that you’re attempting to send from has been banned.
To delist the address, email [email protected] and provide the full NDR code and IP address to delist.
For more information, see Use the delist portal to remove yourself from the blocked senders list.