Microsoft won't delist my IP

Thales Cardoso 21 Reputation points

Hi, we have our email server on premise, with 2 ISPs (1 as the main link and 1 as the failover). Also, I had this problem on our main IP too, and fixed the issue following the same steps described below.

About a year ago we got a new failover IP and we're not able to send any emails to Microsoft through the new IP.

Many email providers don't seem to mind the new IP, including Google (gmail), but on my personal account (hotmail) I can't receive anything, just a bounce email saying

host said: 550 5.7.1
Unfortunately, messages from [X.X.X.X] weren't sent. Please contact your Internet service provider since their network is on our block list (S3150).

Upon further investigation (checking for the IP on ), I found out that my IP was blacklisted for SPAM back on 2017, so I went through all the authorities requesting to drop us from their blacklists, and they did (confirmed by email and again checking on

The only piece that seems to be missing is to request Microsoft to delist us, but going to doesn't show any results, they just deny my requests without further explanation saying

The request to delist IP address X.X.X.X has been denied, and we have escalated your request to Microsoft Support.

DNS seems to be set correctly with SPF, DKIM and DMARC, and the ISP already set the PTR to point our domain to the failover IP, what am I missing? What should I do? I'm very confused.


PS: The tag on the question might be wrong, sorry about that

Not Monitored
Not Monitored
Tag not monitored by Microsoft.
36,928 questions
{count} votes

Accepted answer
  1. Dillon Silzer 54,846 Reputation points

    Hi @Thales Cardoso

    From a similar post found at

    Try filling out the following form found at ( Delivery Team support request)


    If this is helpful please accept answer.

1 additional answer

Sort by: Most helpful
  1. Thales Cardoso 21 Reputation points

    Try filling out the following form found at ( Delivery Team support request)

    Thank you @Dillon Silzer !!
    I filled the form that you linked and they solved my problem!

    After a little back and forth they managed to delist me, took 24 hours to propagate the configuration, but it's a win!

    Again, sorry for the wrong tag/forum, there is not much help out there for this stuff, at least not that I could find.

    0 comments No comments