I think our dedicated sending IP has been blocked solely by Office365. We have stellar sending IP rating, and zero spam reports, content clean, full opt-in etc.

No issues with any other Microsoft client - and we are Return Path certified.

Is there a simple way to check if they have blocked our IP...and if true...how to delist?


2 Answers 2


To state the obvious you can test if office 365 is blocking your emails by creating a 30 day trial.

If your emails are being blocked then you need to address the issue why, which is how they are getting marked as spam. There are plenty of questions related to preventing email being classified as spam already on Pro Webmasters. Then you would either need to contact Microsoft or wait until their spam algorithm unmarks your email address or IP (please do not ask about their algorithm, its unlikely anyone knows other than Microsoft).

  • Hey Simon - Thank you. I already have done exactly that. We have submitted two support tickets with no response, what avenue do you think is the best to pursue in getting someone to respond? Even ReturnPath has been no help to us, although they constantly market their special Inbox placement with Microsoft. Our Return Path score is a 97 with almost nonexistent spam reports...and we have no deliverability issues with any other ISP. Just stumped on how to get this resolved. Appreciate any insight.
    – AdamB
    Nov 21, 2015 at 0:28

Take a look at your email server logs. You should see a message indicating that the client host has been blocked by a blacklist and that your IP has been banned. When you send the email you should also get a non delivery report back from Microsoft.

If you are blocked by the blacklist you can email [email protected] and include your IP address that emails are being sent from and they can start the process and tell you what you need to do to be delisted from the blacklist.

If you haven't been blocked take a do a DNS dig and check what the MX records are for the specific domains you are trying to send emails to and do a trace route as there could be an issue before the mail servers, unlikely but still possible.

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