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Microsoft Defender for Office 365 Blog
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Strengthening Email Ecosystem: Outlook’s New Requirements for High‐Volume Senders

Puneeth's avatar
Puneeth
Icon for Microsoft rankMicrosoft
Apr 02, 2025

This applies to Outlook.com - our consumer service, which is supporting hotmail.com live.com and outlook.com consumer domain addresses.

April 29th Update - Changes have been made to the action take on messages that do not meet requirements, please see details below. Introduction In an era where email remains one of the most widel...
Updated Apr 30, 2025
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cedblm's avatar
cedblm
Copper Contributor
May 28, 2025

Better ask the question. 
There are multiple requirement and to me especially DMARC is common for a domain and its subdomain.

Does that mean that Outlook rejects mails from the whole domain or if a mail has SPF or DKIM alignment it would be accepted ?

(yes we have multiple parties sending mail from their systems where SPF/DKIM is important)