change Undeliverable email messages auto reply

Emil Klöfverskjöld
Occasional Visitor



I have a shared mailbox who only the member of the mailbox can email to. 

If you are not a member and email to the mailbox you get an auto reply. 


This auto reply are a bit aggressive and tells the user that she/he are not allowed to email that mailbox. 

I would simply want to change part of that message to be a little more friendly but cant find where i can do so :)




4 Replies

You cannot change the text of default NDR messages in O365, such as the one sent when delivery restrictions are configured on a mailbox. You can add a custom reason via a Transport rule (with a "block the message" action"), but in general those NDRs look not that friendly...

Maybe use inbox rules instead of setting a restriction on the mailbox itself. To accomplish what you’re looking for you could create a rule that would reply with a custom message any time an email is received and then delete the email, except if it is from a member of the allowed group.

You could also add a "Policy Tip" to the shared mailbox with a text like "This mailbox is only for its members". It would be shown to the users before they are sending the actual email.

Hi Emil


I would prefer creating a Transport rule and adding a disclaimer there to achieve this.




Robin Nishad