Emails are being blocked by hotmail

  • Posted August 13, 2020
  • Email

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))

At here link you can find an answer to the Hotmail problems you are looking for.

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)

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?


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.

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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 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.

no. it never worked

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

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

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.

Regards, KFSys

Running into the same issues. Individual server admins can follow all the EMail deliverability best-practices in the world… and STILL end up on blacklists if they’re listing the larger IP range that part - typically due to their upstream provider (Digital Ocean in this case) having a consistent track record of negligence in addressing issues with spam/network abuse. Which, sadly, does appear to be the case with Digital Ocean, at least judging from the fact that they’re one of the larger sources of spam we receive (top 5 at least), while also being one of the least-responsive to spam complaints.

This is clearly Digital Ocean’s problem to fix, and until they do their services are effectively useless for EMail hosting.

Not only DO is blocked by, also AWS. Even on Azure outbound traffic destined for port 25 is blocked preventing operation of mail server. On Azure you need to get MS approval to operate a mail server and this approval is not given to accounts on the free trial subscription.

The bad news is that the entire ASN of the Digital Ocean network is blocked by Microsoft, likely due to high spam scores on some block lists, more specifically UCEPROTECT-NETWORK at Level 3. This is due to 2 main issues:

  1. Many customers have bad email DNS settings, not implementing DKIM, SPF and DMARC records correctly.
  2. Digital Ocean does not have strict policies to penalize those customers who do not do the right job to prevent the spread of spam, or who deliberately send spam using its network.

The good news is that something is being done, because on the UCEPROTECT website, when searching your ip, you will see a graph that shows a constant decrease in the impact of this ASN on the spam score, and as far as I understand the evaluation of this ASN is almost arriving in the limit, that is, if it continues like this we will soon leave the block list.

To be clear, this block list works on 3 levels, namely: Level 1: Specific IPs are blocked; Level 2: IP ranges are blocked, more specifically the last layer of the subnet; Level 3: The entire ASN is blocked, which is our case;

We need to keep in mind that this situation is caused by both sides and we as customers must do our part to avoid blockages, at all levels. In my case, we had already implemented DKIM and SPF, but we had a simple DMARC record. We created an email to receive the reports and configured accordingly. We are analyzing the results to make this setup perfect. We will soon change DMARC to reject non-validated messages.

Please contribute this content, open calls in DO to force the engineering team to solve the problem on their side, while helping the community to understand the gravity of the situation and encourage us to do our part.

If any information I have mentioned here is inaccurate, please contribute, we need to get out of this dark zone.

Some important links:


Looks like this issue will never have a solution on D.O. side, no matter how good our mail server reputation gets. Did anyone notices if this is related to IP adresses from a specific region? Maybe taking the server to other less used region could prevent this problem or is MS blocking all IP ranges from D.O. globally?

Can anyone suggest an alternative email service or alternate solution to this problem?