Outlook.com Is Quietly Rejecting Email from Domains Without DMARC

Re:Outlook.com Is Quietly Rejecting Email from Domains Witho... by cyrusmg on Monday November 09, 2026 @07:46AM (#50424845)

Since yesterday my email started getting blocked. Does anyone know what's going on ?

  5.4.1 smtp; 550 5.4.1 Recipient address rejected: Access denied.
  For more information see https://aka.ms/…ors
  <redacted>.eurprd02.prod.outlook.com 2026-11-08T19:48:58.651Z <redacted>]

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Re:Outlook.com Is Quietly Rejecting Email from Domains Witho... by dwm on Monday November 09, 2026 @08:36AM (#50425413)

You could consider following the URL in the bounce message. Or searching online for the particular error code, which quickly turns up:

https://learn.microsoft.com/en-us/troubleshoot/exchange/emai...

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Re:Outlook.com Is Quietly Rejecting Email from Domains Witho... by cyrusmg on Monday November 09, 2026 @08:45AM (#50425522)

Thanks!

Some additional context: - I checked online and they do have this email address listed on their pages - This affected 2 separate domains served by Microsoft - I sent them an inquiry email now from my @gmail.com and no bounce was returned so far

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Re:Outlook.com Is Quietly Rejecting Email from Domains Witho... by jeroenhd on Monday November 09, 2026 @11:23AM (#50427705)

Check blocklists for your domain and IP address (and many ASN if you're sending to certain MS servers). The DMARC change has a specific error message ("Message lacks SPF/DKIM/DMARC Auth Records").

Or whoever you're emailing has blocked you for some reason; perhaps your email was marked as spam before, or you/your mail server/your automated tooling has ignored bounces and has crossed a mail server threshold.

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