Yeah, my client got this with both SPF and DKIM. We’re checking to see if there was an error with the DKIM signing from the problematic ESP, but the current evidence I have says that the mail is being signed correctly and Microsoft is just being broken again.
laura > On 3 Mar 2026, at 17:11, John Quaglieri via mailop <[email protected]> wrote: > > 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/. >> >> 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"; <http://www.strath.ac.uk/>, but apparently MS >> knows better and I'm wrong. >> >> I'd be happy to read suggestions on: >> >> How to make the form accept my website address >> Which "issue" the form suggests they are aware of and investigating >> 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]> <mailto:[email protected]> >> on behalf of Lukas Adrian Kron via mailop <[email protected]> >> <mailto:[email protected]> >> Sent: 03 March 2026 12:10 PM >> To: [email protected] <mailto:[email protected]> <[email protected]> >> <mailto:[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] <mailto:[email protected]> >> https://list.mailop.org/listinfo/mailop > -- > John Quaglieri > _______________________________________________ > mailop mailing list > [email protected] <mailto:[email protected]> > https://list.mailop.org/listinfo/mailop -- The Delivery Expert Laura Atkins Word to the Wise [email protected] Delivery hints and commentary: http://www.wordtothewise.com/blog
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