Microsoft blocking mail from some cloud providers

I did, I wiped the server and started over, worked like a charm, email worked out of the box. Did not, unfortunately, fix the original issue I was having (ie. Microsoft mass blocking emails from cloud server platforms, apparently), but that’s ok, I will try another host. :slight_smile:

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I find it interesting, and slightly amusing how people keep saying that cloud providers are blocked by folks like Microsoft…

The truth is, it’s possible to send to virtually any provider through cloud based servers (vps) if you know how to address blocks. We for instance run a cluster of 8 vps’ which send out over half a million messages each month.

From time to time, we get blocked by a big player like Microsoft, but usually this is something we did unintentionally and their system is merely observing the bad behavior and protecting their network accordingly.

Once we’ve resolved the underlying issue, the block is either lifted automatically or through communication with their postmaster team.

The same issues we face in the cloud, we used to face while managing dedicated servers, so to say that a cloud provider is more likely to be blocked isn’t an accurate assessment IMHO. It comes down to:

  1. Do you know how to manage an email server?

  2. Do you understand why you’ve been blocked?

  3. Do you know how to resolve the underlying issue?

  4. Do you know the steps with the specific ISP on how to get unblocked?

Taken from experience, it’s easy to assume that putting an email server online is a “set it, and forget it” process, but the truth is, if you’re not maintaining the server, you’re bound to get blocked at least a few times by neglecting your duties.

In today’s DMARC-enabled world, it’s even easier to get blocked if you don’t take precautions, and address things pro-actively, as well as re-actively.

*** email hosting is a pain to maintain, but sometimes a necessary evil. ***

Best Regards,
Peter Knowles | TPN Solutions

Well, since this is a specific recent issue that is happening with ips that have no history at all, I would have to say you’re wrong. Ionos just had to deal with this 3 days ago:

Digitalocean, which is where my client hosts their vps, has not yet addressed this. Thank you for your feedback though.



When you say “no history”, do you mean these IPs were recently issued to you? If so, there are two things to take into consideration…

  1. The IPs are not likely unused, they were likely used by a former party who may have dirtied them before you were given them. Sadly, people dirty IPs, then just dump them either because they don’t want to deal with cleaning up their reputation or don’t know how to.

  2. The IPs have not been used with email hosting in a while, or ever. In this case, you need to “warm them up” by sending out small batches of emails, progressively increasing. This is because the ISP has not yet established a reputation with you, or it’s been a while since they have, so they tend to trust the IPs less and will either rate limit, or impose temporary blocks if you suddenly throw lots of mail at them in a short period of time.

*** BTW: Our 8 node cluster which I spoke of earlier, that successfully sends to Microsoft and many other top tier ISPs – which we’ve also muddied up, then cleaned up – is hosted by Digital Ocean ***

Best Regards,
Peter Knowles | TPN Solutions

Peter, @mvandemar is right. Microsoft is in the middle of some kind of mess with their spam-blocking system for several months now. I’ve had IP’s with perfect records on SenderScore blocked by Microsoft for excessive spam, when even their own FBL confirms that there was no spam at all sent. One was an IP that has exactly two mail users: myself and my elderly father, who barely knows how to check his mail, much less spam anyone.

Submitting a remediation form typically results in denials by three dumb robots and two even dumber humans stating that the IP’s are “not eligible for remediation.” Apparently they don’t have access to their own company’s FBL, or they would be able to see that there were no spam reports filed.

What I’ve been doing is replying to the second dumb human with a message of my own informing them that I’m blocking all incoming mail from,,, and (and actually doing so); and advising them that their domains are not eligible for remediation due to excessive amounts of spam through those domains. That typically gets the issue bumped upstairs to someone who can actually do something about it.

But MS is definitely having problems in this area. They’re blocking IP’s for no reason at all. Personally, I don’t really care very much because most hotmail users in particular are either spammers or idiots; but it’s a very big problem for people who actually care.


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I never said it was easy to get unblocked, but yes it is possible. I have servers that get blocked, and unblocked by the likes of Microsoft all the time. Sometimes it takes a little extra effort, and the right person managing the request on their end, sometimes even including the FCC in the conversation.

Bottom line is, email blocks happen. But if you address the underlying reason for the block, and/or get into a professional discussion with the ISP, you can get the blocks removed.

“If at first you don’t succeed, try, try again”

Best Regards,
Peter Knowles | TPN Solutions

But if you address the underlying reason for the block, and/or get into a professional discussion with the ISP, you can get the blocks removed.

Actual quote in the 6th email they sent me when I was trying to get my own server unblocked: “I do not see anything offhand that would be preventing your mail from reaching our customers.”

This was followed by the normal canned response instructing me, “How Not to Spam” despite me informing them multiple times that I do not send out any marketing materials. None, nadda, zip, zilch, zero. I have no mailing lists whatsoever.

(This thread has run far afield of the original topic, maybe we should start, or find, a thread on the Microsoft forums instead, allow others with the same frustrations to chime in, and not clutter Virtualmin with off-topic chatter…)


I moved this whole discussion off of the original thread because it had gone wildly off-topic of the original title. Y’all know I hate that. :wink:

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Appreciate ya @Joe, thank you for all you do! :slight_smile:


The problem is that they’re blocking well-established IP’s with absolutely zero history of spam complaints, whose admins have even enrolled in Microsoft’s useless FBL; and even when the agents agree that there’s no history of spam complaints, they can’t do anything about it.

So you wind up having to resort to threats or countermeasures (like FCC complaints or blocking their domains) to “mitigate” something that should have never happened in the first place.

The datacenter techs seem to have an inside line to people at MS who can correct the problem. It still takes a couple of days, but eventually it gets done. Ordinary server admins may as well be pissing into the wind if they follow the prescribed procedures. Even if the flunky-level techs agree that there’s been no abuse, they’re powerless to do anything about it.

They’re also presumptively blocking IP’s that have no reputation one way or the other, which is idiotic. (Although I have to admit that I’m surprised there are any such IP addresses, at least as far as IPV4 is concerned.)

In any event, IP’s should be automatically rehabilitated and start with a clean slate whenever the PTR changes. I mean, I’m an idiot, and I managed to code automatic rehabilitation into the blocklists that I maintain. MS can’t do the same?

The threats tend to work at getting the tickets bumped upstairs, though. I will say that. They take offense to their users’ mail being blocked, which is ironic because MS is the number one offender in terms of the sheer bulk of spam sent from their domains.


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