Microsoft Office 365 Smart Host Addresses

We recently had an issue where we thought Microsoft might have changed the allowable smart host IP address that we were using. After some digging it turned out to be a blacklist issue but during the investigation I found that Microsoft has a public listing of their IP address availabile.

View the Exchange Online Protection IP Addresses at

Check to see if you are on any blacklists by entering your public IP address with MX Toolbox at  or Black List Alert at .

Read this article from which provides details on how to get removed from a Microsoft blacklist at or this article from

If you or your company are sending unsolicited emails or general spam – you’ll need to clean up your internal practices before taking the steps below, or Microsoft will promptly deny your request, or they’ll process it and you’ll find yourself being blocked again right away. That said, you can request removal you will need the following information:
Grab the log entry with the specific error message or the (NDR email if you received one) from your email server.

  • You’ll need the IP address of your email server (the sending IP address).
  • You’ll probably need your IT team’s assistance to get this info.
  • You’ll also need the email address you sent the email to and the send-from.
  • Ideally, include a copy of the email.

Once you may request delisting by sending an email to delist -at- (of course replace the -at- with ‘@’ to make it a real address) with the above information, including the IP address you want removed from their list. If you’re a Microsoft Hosted Exchange customer, you can also try sending the above info to: false_positive -at-

Good luck getting your email flowing and let me know of any other tips in the comments.



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