Cannot send emails to Microsoft server users

Emails from my Cloudflare domain cannot be sent to Microsoft users.
It has been a serious problem for over 2 weeks.
Weird thing is that I didn’t receive any bounce mails with error messages, it seems that my emails just cannot reach them at all.
Is there anything that can be done on my side?
I have added SPF record, do I need to change other settings in DNS?

Can you check your email with and share the result here?

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Thanks for advice. I tried 2 times(including reloading) but all failed.
About 2 months ago my team was able to send emails to microsoft users, but suddenly the problem occurred without any hint.
My web host replied that there was no change in settings so far, and Microsoft support team replied that our outbound IPs are not blocked as well.
Could you advice what should I check for the next step?

How do you mean? The test didn’t work? Or did the test work but the result was “fail”?

In that case, it would be really helpful if you shared a link to the test result.


The result page shows “We didn’t get your email.”, so I guess the email didn’t reach the testing mailbox.

That’s weird. But you can send email to others, just not to Microsoft?

I’ll send you my mailaddress via pm, can you try sending me an email?

Yes, other server users can receive our emails (like gmail), but only Microsoft users block.
We just sent an email, so please check your mailbox.

Your email did reach me, but UCEPROTECT shows quite a lot of spam coming from your host.

Microsoft is known to be quite aggressive in blocking spam, so it is quite possible they blocked your host’s entire network.

You should probably consider getting a professional email service to avoid such problems.

Thanks for your advice!
Could you tell us where we can get information or kinds of report of UCEPROTECT you mentioned?
We will check details with our service provider.


UCEPROTECT provides several levels of IP listings, such as e.g. Level 1, meaning that it is your exact IP address that was the culprit and delivered the spam message(s) that has been seen.

Level 2 and above are signals covering IP range/neighbourhood (a listing of more than just an individual IP address), and Level 3 (a listing of your entire ISP).

You can look up your mail server’s IP address with them.

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Thanks for your reply. I will check these things with our mail service provider.