Tenant restricted from sending email

Question

Hello

Please i need your help on this issue.

We have received alert that our email service has been barred "Tenant restricted from sending email". Last night we had issue, and this might have contributed to large number of email alerts generated from platform. Could this service be restored at earliest.

 

Here is the error message of the email we received:

Then when trying to send an email i get this error message below:

Answer 1

Based on your description and the NDR your provided, "550.5.7.705" tenant has exceeded threshold. In general, it means the O365 user in your tenant sent bulk emails in a period, and then it was detected as spam. So, it may result in your tenant was blocked in O365.

May I know is there any new connector or relay has been set up at your end? If yes, please verify your connectors/relay has no issue with email routing.

Please check if the emails sent by the user is legitimate. Please explain to user that O365 does not support bulk sending of emails beyond the limits.

If the user claims that he did not send the email, check if is there any user and admin accounts potentially compromised.

For this, refer Determine whether Microsoft 365 account is compromised - Microsoft 365 | Microsoft Learn.

You could also refer to NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750 - Exchange | Microsoft Learn for more information.

 

As you want to restore service at earliest, I suggest you could open a service request ticket in the O365 portal, and then delivery the related information to Microsoft higher engineers to help release your tenant from O365 backend.

If you have any questions, please feel free to contact me.