Unable to Send or Receive Emails Due to Tenant Threshold Exceeding Limit

Hi, @Oualid Abdellaoui

Thanks for posting your question in the Microsoft Q&A forum.

According to your description, you are experiencing the error "Cannot send or receive email because the tenant threshold has exceeded the limit". I would like to confirm with you what your specific error message is? If the full NDR error message is "5.7.705 Access denied, tenant has exceeded the threshold". You can try the following steps to resolve the issue:

1. In the test you described, you saw the error caused by an automated program constantly sending emails to your personal email. This may be because your organization sends too much spam or bulk mail and Exchange Online blocks your outgoing mail. You can refer to the following links and check the information to try to solve:

Protect and recover email capabilities for infected Microsoft 365 accounts and mailboxes,

Set up multi-factor authentication for Microsoft 365,

Configure Microsoft 365 tenants for increased security and improve security with Microsoft Secure Score.

Reference: NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750 - Microsoft Support

2. If you are not an administrator, you need to contact your organization's email administrator and have them try the above steps to remove unknown connectors (such as the Automaton you mentioned) that may be used to send emails using your tenant.

If you have any questions, please feel free to contact me. If the answer is helpful, please click "Accept Answer" because it can help other members of the Microsoft Q&A community who have encountered similar problems and are looking for solutions. Thank you.

Best,

Jeanne