Emails are being blocked by hotmail

Posted August 13, 2020 41.3k 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
  • I have the same issue - new server, 10/10 on, I can send emails to every other provider I have tried so far. It would be great if Digital Ocean could get in touch with someone at MS to try to get this resolved. The message clearly states part of Digial Ocean’s network is on their blocklist, and multiple customers are reporting the same issue so it seems like they are just blocking Digital Ocean IP addresses.

    This is a real roadblock.

  • Hi…
    My email server is blocked too… How i can fix it?

    Where can I contact Digital Ocean support staff to guide me or solve my problem?


  • Huge problem, which I can’t do anything about as a DO customer. Seems that DO must take action, because they own the IP ranges in question.

    <***>: 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 (S3140). You can also refer your provider to
    [] (in reply to MAIL
    FROM command)

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16 answers

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!

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.

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.

  • you still do not solve the problem?,I have validated spf, dmarc and dkim, the emails are sent with a score of 10/10, in gmail everything is perfect

    • Hi all,

      Hotmail usually have a policy to block IP addresses based on Nothing. In this case, what I do is contact Hotmail until they respond to me and remove the block on my IP.

      • @KFSys They’re saying in the bounce emails that they are blocking part of the whole network, not just a single IP address:

        Unfortunately, messages from [] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). 

        Brand new server, just set it up today.


I’m trying my luck with

Not hoping on it though - this seems like a larger issue for DigitalOcean to resolve - MS blocking entire DO IP ranges due to the amount of (spam) misuse coming from DO.

I’m new to setting up email with Postfix set up on Digital Ocean droplet now. Running through the checks at may be helping. It goes through SFP, MX and other records, I’m guessing anyway if fix these , Hotmail will accept it. My spam score is now a terrible 1.7/10 so this site seems to help work on that. It is interesting that I could send to yahoo and gmail addresses both got o the inbox though, not sure if Hotmail may be doing right though to be strict.

Hotmail blocks all IP ranges of all cloud/vps providers by default. Now they are requiring actual ownership of the IP address of your mail server to get it removed:

“In-order for us to investigate further, please provide the required documents (email from ISP as PDF attachment and Invoice copy) supporting the Proof of Purchase for the IP.”

Without actually owning the IP block (not just renting it or being assigned from your VPS provider) they will refuse to unblock you.

Despite this policy, as a Hotmail user, I still receive many obviously spam emails. Additionally, as a Gmail user, I don’t receive any spam emails and they do not block my private mail server which is hosted on a VPS.

I believe Microsoft is a euphemism for Bill Gate’s penis.

Huge frustration!

My data center crashed last friday so I have spent all days since, to move me and my clients (20 web and mail domains) to Digital Ocean, cause I thought that was “the state of the art”.

Now it turns out that we can’t email Hotmail addresses, and 90% of the mail is marked as spam… :(
I have asked for whitelisting of my IP, to no avail.


  • Will I not be able to mail to Hotmail no matter how good mail score I am able to manage, because the mail server is within DO’s IP range?
  • If I would be able to do that, is there a good guide on all SPF records, and other measures to take, you need to setup in best possible way?
  • If nothing of this is true, do you have any other Mail Service Provider to recommend? I am based in Sweden, if that matters.

Please help!

Same problem for my servers. All 3 have same problem - IP blocked by HOTMAIL. Everything works perfect 10/10 email test score. Nothing else to do. It seems that Hotmail has problems with DO network.

Any fixes for this yet?

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