It's been mentioned several times here already, but Microsoft has had
known issues with DNS timeouts related to DKIM verification for a very
long time now. You're likely just now experiencing it more directly with
their recent policy changes.
Over 99% of ${dayjobs} DKIM verification failures (numbering in the
millions) are from specifically OLC, outstripping all other DMARC
reporting receivers combined. Even upping TTL has almost no effect
unfortunately.
- Mark Alley
On 5/14/2025 8:45 AM, Fernando MM via mailop wrote:
Hi everyone,
Is anyone else experiencing intermittent DKIM failures when sending
emails to Outlook.com? This started on May 5th.
If I resend the same message, it’s successfully delivered. By “same
message”, I mean the exact same content, headers, Message-ID, DKIM
signature, etc. Essentially copy/pasting the original message without
any modifications.
Even other messages sent in the same SMTP connection and using the
same sender/DKIM key are accepted.
The error message I receive is:
```
550 5.7.515 Access denied, sending domain REDACTED-FOR-PRIVACY.COM
<http://REDACTED-FOR-PRIVACY.COM> 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 [SA0PR11MB4544.namprd11.prod.outlook.com
<http://SA0PR11MB4544.namprd11.prod.outlook.com>
2025-05-13T15:54:59.356Z 08DD91CC42BDD986]
```
DKIM is correctly configured. I’ve verified it using multiple tools
(e.g., https://aboutmy.email/, opendkim-testmsg, etc.), and we have
zero issues with other providers. DMARC is set as "v=DMARC1; p=none;".
I’ve opened a support ticket, but the responses so far have been
generic and not directly related to the intermittent nature of the issue.
Anyone else seeing something similar?
Best regards,
Fernando.
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