I've noticed that Microsoft's systems fail intermittently to
validate DNS lookups for DMARC, SPF, DKIM, and PTR records. Some
users have become accustomed to trying again later to get their
eMails through (which is not ideal).
Although it doesn't happen very often, Microsoft's systems have been
doing this since last year (and possibly earlier than that), and it
doesn't seem to target any particular providers (e.g., a few of my
clients with GMail accounts have asked me what the errors mean when
they've received bounce-backs just like the one that you included).
Feel free to send some test messages to
[email protected] from that address if you want to
confirm that your DKIM is working -- they'll be rejected if it isn't.
> Here's a summary of an SMTP rejection from Microsoft. I am quite sure
> that the message had a valid arxiv.org DKIM signature and was sent
> from an address in the SPF record. Anything I can do about it?
>
> We've been sending this person mail for years at an outlook.com.au
> address and nearly all of them have worked, including several today.
>
> 550,5.7.515,Access denied, sending domain ARXIV.ORG 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 [SY8P300MB0731.AUSP300.PROD.OUTLOOK.COM
> 2026-05-08T18:21:38.150Z 08DEAD0640C37A36]
> [MW4PR04CA0059.namprd04.prod.outlook.com 2026-05-08T18:21:38.232Z
> 08DEACE91EBF534A] [MW1PEPF0001615B.namprd21.prod.outlook.com
> 2026-05-08T18:21:38.253Z 08DEACF5EA686851]
>
> R's,
> John
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--
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Randolf Richardson, CNA - [email protected]
Inter-Corporate Computer & Network Services, Inc.
Vancouver, Beautiful British Columbia, Canada
https://www.inter-corporate.com/
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