On Wed, Feb 25, 2026 at 9:33 PM postfix--- via mailop <[email protected]>
wrote:

> Sorry to read of your woes, but I am happy that one of the oligopolists
> is shaking the tree and causing pain to the whole industry.  Because it
> is time for the industry to stop the growing VOLUME of emails and focus
> on QUALITY.  Less is more, despite technology's advancement that makes
> more verbal diarrhea (LLMs) and feed it to the same limited number of
> human recipients at higher frequency.  ACCEPT THAT YOUR MARKET HAS GROWN
> BEYOND USEFUL SIZE AND NEED A HEALTHY SHRINKING.
>

You seem to assume that everyone sending email to recipients on outlook is
sending marketing email.   There are lots of us who send email for entirely
non-commercial reasons, and others who are sending commercial but
non-advertising email.  And then there are people's ISPs, who aren't
originating any email at all, simply delivering mail from their users to
Microsoft's users.

As far as I can tell, Microsoft does not distinguish between any senders,
regardless of the type of email.

In my case (I started the thread that got killed on the weekend), I host an
~1800 subscriber technical mailing list, similar in function to this list,
that averages single-digit emails per day, and has under 200 subscribers
with their mail on outlook.com MX servers.  Outlook randomly started
blocking mail from that list to recipients using outlook.com mail servers,
along with transactional email from our self-help portal and the chat
server we run (people trying to do password recoveries, or signups), and
human-sender email from our staff to individuals with outlook mailboxes.
 Email from us to Outlook isn't high volume.  I imagine by the standards of
most of this lists's subscribers we barely register as a rouding error.

To be absoolutely clear, as far as I can tell we have never received a
response from an outlook.com mail server indicating we're being rate
limited.

And yet, we were blocked.  And when I heard from Outlook's mail support,
they simultaneously claimed:
- they couldn't find any indication that our IP address was blocked
- the block on our IP address has been mitigated (these seem mutually
exclusive, but maybe I'm missing nuance)
- and "I am unable to provide any details about this situation since we do
not have the liberty to discuss the nature of the block" (a direct quote on
the subject of the definition of the S3150 error).

So they won't or can't admit we were blocked (but they're also willing to
unblock us as long as we ask!), and they're outright refusing to tell us
what caused the block, so we have no way of knowing how to avoid being
blocked in the future.  This isn't "shaking things up"... this is being
actively hostile to legitimate senders.
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