Thanks for the info, Mark. It’s good to have confirmation that we’re not
the only ones experiencing this.

Best regards,
Fernando.

On Wed, May 14, 2025 at 11:17 AM Mark Alley via mailop <[email protected]>
wrote:

> 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
> 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
> 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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