I saw a similar error this weekend (Spf= Pass , Dkim= Fail , DMARC=
Pass) and from what I gather certain domains now have a requirement for
both dkim and spf. Hotmail indicates 5,000, but not the time frame, and
I believe it is longer than per day as the domain I saw it on doesn't
send that many messages to outlook/hotmail per day. Once dkim was added
the message went through.
On 3/3/2026 11:52 AM, Jethro Binks via mailop wrote:
All,
We were seeing these temporary deferrals for MS-related consumer
domains from time to time in the last couple of weeks, after maybe a
couple of days it would clear up and messages would be delivered onwards.
However starting on 27th Feb we've got something different. Full hard
rejections with: "550 5.7.515 Access denied, sending domain
STRATH.AC.UK doesn't meet the required authentication level. The
sender's domain in the 5322.From address doesn't meet the
authentication requirements defined for the sender. To learn how to
fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf=
Pass , Dkim= Fail , DMARC= Pass"
For the particular server of ours that's involved in this (we've been
sending from its IP for maybe 15 years), we are not doing any DKIM
signing for Reasons. I had thought (rightly or wrongly) that either
of SPF pass or DKIM pass was fine, that's certainly been the situation
up to now. Something's changed somewhere though lately.
Well, anyway, I thought I'd take one of the suggested routes in the
forums and report at https://olcsupport.office.com/
<https://olcsupport.office.com/>.
There's a big banner at the top: "We are aware of an issue that may
result in certain IP addresses being temporarily rejected at higher
rates. We are actively investigating the issue. Please continue to
submit tickets if you are experiencing this problem.". Is that the
temporary defer problem? Or the permanent reject one? Or some other
problem? No idea, so I'll fill the form in anyway.
Except, I can't submit it. I get the error: "Website URL must start
with http:// or https:// and contain a valid domain and top level
domain.". I'd like to think I'd know my website address
is "http://www.strath.ac.uk";, but apparently MS knows better and I'm
wrong.
I'd be happy to read suggestions on:
1.
How to make the form accept my website address
2.
Which "issue" the form suggests they are aware of and investigating
3.
Whether I can no longer avoid DKIM signing messages and must stop
relying on only SPF
(And I see https://aka.ms/postmaster is still broken).
Jethro.
. . . . . . . . . . . . . . . . . . . . . . . . .
Jethro R Binks, Network Manager,
Information Services Directorate, University Of Strathclyde, Glasgow, UK
The University of Strathclyde is a charitable body, registered
in Scotland, number SC015263.
------------------------------------------------------------------------
*From:* mailop <[email protected]> on behalf of Lukas Adrian
Kron via mailop <[email protected]>
*Sent:* 03 March 2026 12:10 PM
*To:* [email protected] <[email protected]>
*Subject:* Re: [mailop] Outlook rate limiting, just us?
Something did change indeed.
We, as a small volume sender are seeing 451 4.7.650 S775 errors for
the first time.
No blockage. Maybe they switched over from sending the 451's to any IP
in the /24
and actually sending it to the IP.
But just a thought.
Mit freundlichen Grüßen
Lukas Adrian Kron
Geschäftsführung
Bitte denken Sie an die Umwelt, bevor Sie diese Nachricht drucken.
[email protected] <mailto:[email protected]>, www.lugges.eu
<http://www.lugges.eu>, +49 2302-9838905
lugges UG (haftungsbeschränkt), Heintzmannstraße 174
44801 Bochum AG Bochum HRB 19066, GF.: Lukas Adrian Kron
Am 24.02.2026 um 14:47 schrieb Dominique Rousseau via mailop:
Le Tue, Feb 24, 2026 at 12:45:09PM +0000, Gellner, Oliver via mailop
[[email protected] <mailto:[email protected]>] a écrit:
Microsoft's spam handling is broken, simple as that. No need to
argue about that.
We receive the same error messages for all servers since 2026-02-23
18:45 UTC. It's unlikely that Microsoft suddenly received spam from
all IP addresses of all kind of unrelated organizations yesterday
evening. Probably some algorithm went nuts there.
Browse the list archives.
Those errors when sending to "outlook" adresses run for a while now.
Seems like they made new rules with dynamic throttle, which nobody
understands for now.
For the servers (low volume) I run which encountered the probleme I
limited to one SMTP connection every 10s.
( which would probably bothersome for quit high volume sender, OK for us
)
_______________________________________________
mailop mailing list
[email protected]
https://list.mailop.org/listinfo/mailop
--
John Quaglieri
_______________________________________________
mailop mailing list
[email protected]
https://list.mailop.org/listinfo/mailop
