Microsoft 365 services for external email senders

Email abuse, junk email, and fraudulent email (phishing) continue to burden internet email. To help maintain trust in the use of email, Microsoft uses several features to help protect our users. However, we understand the importance of not affecting legitimate email. Therefore, we have a suite of services to help external senders proactively manage their sender reputation and improve their ability to deliver email to Microsoft 365 users.

This overview provides information about the benefits we provide to your organization, even if you aren't a Microsoft 365 customer.


If you're not a Microsoft 365 customer, and you're trying to send email to Microsoft 365, this article is for you. If you're an admin in Microsoft 365 and you need help with fighting spam, this article isn't for you. Instead, see anti-spam and anti-malware.

Microsoft support

Microsoft offers several support options for people having trouble sending mail to Microsoft 365 recipients. We recommend that you:

  • Follow the instructions in any non-delivery report (also known as an NDR or bounce message) that you receive.

  • Check out the most common problems that external senders encounter in External senders - Troubleshoot email sent to Microsoft 365.

  • Check the Microsoft community forums.

  • Ask the Microsoft 365 recipient to contact Microsoft Support and open a support ticket on your behalf. Typically, external senders can't open support tickets in Microsoft 365. But, there are legal reasons that might require Microsoft Support to communicate directly with owner of the blocked source IP address space.

    For more information about Microsoft Technical support for Microsoft 365, see Support.

Anti-Spam IP Delist Portal

This self-service portal at allows you to request your removal from the Microsoft 365 blocked senders list. Use the portal if you get errors sending messages to Microsoft 365 recipients. For more information, see Use the delist portal to remove yourself from the blocked senders list.

Abuse and spam reporting for junk email originating from Exchange Online

Third parties occasionally violate our terms of use and use Microsoft 365 to send junk email. If you receive junk email from Microsoft 365 senders, you can report these messages to Microsoft. For instructions, see Report messages and files to Microsoft.

The following article explains how external organizations can avoid having their email blocked by adhering to our anti-spam rules, and contains legal stuff that you need to know: External senders - Policies, practices, and guidelines.