Exchange Online: Native external sender callouts on email in Outlook

This is for Exchange Online only (M365):

Today the IOS Outlook app finally got support for “Native external sender callouts”, this means that you will get a “tag” when a sender is “external”, that tag can be clicked and will reveal the email address, this is an attempt to help receipients fight phishing and spam.

This new feature shall replace the transport rules that some have setup earlier, adding a HTML line on the top of every email arriving from outside the organisation.

When implementing this, that transport rule should be disabled!

To set this up


  1. Connect to Exchange Online PowerShell.
  2. Exchange Online tenant admin will need to run the cmdlet Set-ExternalInOutlook to enable the new user interface for the whole tenant (this is available now); adding certain emails and domains to the allow list via the cmdlet is also possible.
  3. Outlook on the web already supports this. Outlook Mobile (iOS & Android) and Outlook for Mac are rolling out this feature. Specific versions:
    • Outlook on the web: available now
    • Outlook for Windows: available in May 2021 (starting with Insider Fast)
    • Outlook mobile (iOS & Android): version 4.2111.0 and higher
    • Outlook for Mac: version 16.47 and higher

Here it is enabled for the whole organisation:

Set-ExternalInOutlook -Enabled $true”

Outlook on the web, Mac, and mobile will display an External tag in the message list. Outlook Desktop and OWA will show the sender’s email address at reading pane info bar. Outlook mobile and Outlook for Mac will only see an external tag on the message reading pane, and users will need to click the tag to see the real sender’s email address.

Outlook on the web view of External sender:

thumbnail image 1 of blog post titled 

							Native external sender callouts on email in Outlook

In Outlook for iOS, External sender user interface in the message list, External tag when reading chosen email and view of sender’s email address after tapping External label:

thumbnail image 2 of blog post titled 

							Native external sender callouts on email in Outlook

Once this feature is enabled via PowerShell, it might take 24-48 hours for your users to start seeing the External sender tag in email messages received from external sources (outside of your organization), providing their Outlook version supports it.

If enabling this, you might want to notify your users about the new feature and update your training and documentation, as appropriate.



Set-ExternalInOutlook (ExchangePowerShell) | Microsoft Docs

Native external sender callouts on email in Outlook – Microsoft Tech Community


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