How to Block onmicrosoft.com in Outlook classic on Windows 11?

hi SimplyHuman​ I understand the frustration, but unfortunately there isn't a built-in option in Outlook to block all emails from onmicrosoft.com.

The challenge is that onmicrosoft.com is Microsoft's default domain for Microsoft 365 tenants, and many legitimate organizations use it for mail routing or administrative purposes. Blocking the entire domain globally could also block valid emails.

If Outlook rules aren't matching these messages, it's often because the visible "From" address differs from the actual sender or return-path. One thing you could try is creating a rule based on the message headers or Internet Message Header if the onmicrosoft.com domain consistently appears there.

If you're using Outlook.com or a Microsoft 365 personal account, your filtering options are fairly limited compared to Exchange Online, where mail flow rules can block domains at the server level.

It would certainly be a useful enhancement if Microsoft allowed users to block specific sender domains like onmicrosoft.com at the mailbox level. You're probably not the only one who would find that feature valuable.