Why is Microsoft blocking my email?

Are you having problems sending emails from your VPS to any of Microsoft domains such as Hotmail, Live, Msn, Outlook or any 365 users? Then it’s likely that you have been blacklisted. In most cases, the blacklisting can be fixed by following the steps below. 


First of all, this article is only useful if you’re blocked by the receiver (any Microsoft domain). If this is the case, you've probably received a bounce-message email containing keywords such as: 550 5.7.606 Access denied, banned sending IP (x.x.x.x.). This can happen if you’re sending out SPAM, but, many times the reason isn’t clear. You can easily check if you’re not blocked anywhere else with  Hetrixtools. 


Why Does Microsoft Reject Emails? 

The most common cause for Hotmail blacklisting your email is a security breach, such as a hacked user account or a spam-sending web service. While there are several reasons why Hotmail may block your email, the following are the most typical ones: 

  • Your email volume increased or decreased dramatically
  • Your DNS settings are wrong 
  • You're using a new IP address to send emails 
  • Your DNS settings are wrong 

If you are blacklisted by Microsoft, you have 2 options to apply for a delisting 

1. Send an email to Microsoft:

You can easily send an email to delist@messaging.microsoft.com with the request to delist your IP address. This is only possible for emails to Hotmail and/or Live domains. Microsoft will reply, but it can take up to 48 hours before you get unblocked. 


2. Use the delisting-form:  

If you use the delisting-form, it will ask you to leave some (extra) personal information. This is how to fill in the form: 

Microsoft form 

Your answer 

Issue Title 

Your Issue 

Contact name 

Your name 

What domain are you sending to 


Contact email address 

Your own email address 

Time Zone 

Your Time zone 

What domain are you sending from 

The domain you were using when you sent the (blocked) email 

What would you describe your company or yourself 

Select the relevant option (many times this is ‘others’) 

Outbound IP(s) or range(s) 

The IP address of your VPS 

Is your server dedicated or shared? 

The server is shared in this case 


Copy and paste any error messages 

This means, the bounced header of your email 



Provide the url of your website 



Conditionally mitigated by Microsoft 

After you fill out the form, you should receive an auto-reply confirmation. This can take anywhere from a few minutes to a couple of hours. After about 10 to 12 hours, you should receive a reply telling you the IP has been delisted (conditionally mitigated). If not, you’ll receive an email saying ‘not qualified for mitigation’. 

The last mail is an automated email. So, if you still have some questions, reply the email and ask for more information. The question will be passed on to an actual person at Microsoft who will take a second look. 

Respond to the email if you receive a non-qualified response. Inquire as to why your IP was deemed ineligible. In most cases, you will receive a response within 24-48 hours. The answer is personal and from a real technician who will assist you in resolving the problem. 


If your IP qualifies for mitigation, the Hotmail email restriction should be lifted within 24 hours. 

Important: is the problem specifically related to Office 365? You can use Delist for Office 365.   

In case Microsoft refuses to help You may request assist from our support staff by e-mail (support@tilaa.com) or through the customer portal. 

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Date Votes
  • There's another thing Microsoft did: they blackhole (without sending any delivery failure report) all the mail with DKIM-canonicalization "simple", which is used by the opendkim package as default.

    If you use opendkim please make sure you activate and change this line in /etc/opendkim.conf to let Microsoft accept your emails:

    Canonicalization relaxed/relaxed

  • It seems Microsoft is getting the AS wrong:

    Unfortunately, messages from [<ip>] weren't sent.
       Please contact your Internet service provider since part of their network
       is on our block list (AS3150).

    The IP in question is on AS196752.

  • Actually, the AS is not referring to an Autonomous Network like one would expect, but to an internal Microsoft Anti Spam code. It took us a while to figure that one out.

  • We have open more ticket on https://support.microsoft.com without any good response.

    Currently we are blocked and in the better case we have a delay of 17 our for a email delivery.


    Also we have a good setup of dkim dmark and spf, and we have insert our IP into https://postmaster.live.com/

    of course without solve it!



  • Thanks for the article, this was helpful!

    I tried all the usual things -- check logs for any unusual activity, search for rootkits, etc. -- but am quite confident my server is not hacked. It's just Microsoft being "overzealous".

    Sorry to hear it is affecting others too.

    My (cynical) view is that Microsoft are doing whatever they can to make life impossible for independent mail server administrators, until everyone just switches to their Exchange/Outlook products.

    Tilaa, perhaps you should consider making a formal complaint to competition authorities. This sort of behaviour from Microsoft is neither new nor accidental...

    Keep up the good work!


  • I had the same issue for four days, this is really annoying.. not only hotmail but also gmail. Logged a ticket to the support yesterday, got no reply, so I just tested it again this morning and it is working again for gmail/hotmail. 

    In a new customer migrated my first websites, and immediately issues. This is really bad advertising for you and for me. I see that this is going on for a few months now. Jump into a plane to Redmond, Washington ;-)


    Meanwhile I received a support answer from Tilaa stating: 'Your email is unknown to us, please mail this from the e-mail you used to rent the VPS'....It was sent from my VPS, with an e-mail of my company domainname.


    Makes me sad.


  • Kenny wrote:
    Meanwhile I received a support answer from Tilaa stating: 'Your email is unknown to us, please mail this from the e-mail you used to rent the VPS'....It was sent from my VPS, with an e-mail of my company domainname.


    Actually this makes sense. The problem you are reporting to Tilaa support might in theory be so bad that your VPS isn't usable or accessible at all. In such a case, it would be rather stupid if Tilaa sent their response to the e-mail address which is served in your VPS, as you would not be able to read it.

    That is why Tilaa always registers an e-mail address for each client which is outside the client's domain(s) hosted at Tilaa, and they use that for support first. Thus there is a better chance of reaching the client.


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