Emails are being blocked by hotmail

Posted August 13, 2020 848 views

Emails I am sending are being blocked by hotmail.

Here is the mail log error message:

to=<>,[]:25, delay=0.15, delays=0.01/0.01/0.1/0.04, dsn=5.7.1, status=bounced (host[] said: 550 5.7.1 Unfortunately, messages from [] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to [] (in reply to MAIL FROM command))
edited by MattIPv4

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4 answers

Hi @jeffWhale,

There could be possible reasons behind the experienced behavior. Let’s first start with making sure your domain has the full priority to send out e-mails and getting the highest possible score on e-mails.

First point

Make sure you have configured SPF, DKIM and DMARC records on your domain. Those 3 records prove authenticity for your server and domain. Without these 3 it will be hard to send e-mails as a whole to every big mail provider. You can check the following article for more information:

Once you have the above configured use a mail testing website which will let you know what your e-mail score is. You must make it 10/10. The website I personally use is :

** Second Point **

Make sure you are sending authenticated MAILS. If you are using a script or some webmail gui, make sure you are using SSL/TLS encryption with e-mails going out either from port 465 or port 587.

** Third and last Point **

Make sure your IP address is not blocked and you are not sending out spam messages. You can check your IP address in multiple websites for blacklisting. As for the websites you can search for them in google or any other search website.

If it’s blacklisted, you’ll need to pinpoint where exactly is the spam originating from.


by Pablo Carranza
A carefully tailored SPF record will reduce the likelihood of your domain name getting fraudulently spoofed and keep your messages from getting flagged as spam before they reach your recipients.

it’s a new server. but it’s already blocked by hotmail, microsoft outlook

  • I am currently experiencing the same issue. I’ve got a perfect score using and implementing DKIM, DMARC, SPF plus using valid certificates.

    Let me know if you have any luck!

I have the same problem. The server’s ip is new. My server meets all security specifications and still hotmail blocks the ip. I tried to communicate with them but I don’t get any answers.

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