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Don't all messages show the contact's Teams status?
Are these contacts within your organization? As far as I know, Outlook is currently showing an unknown status for federated (external) Teams contacts.
According to my tests, the status is not displayed directly on the mail page. Try clicking on this user to check if the status is visible.
If it's still not visible, for this problem, please try restarting your Outlook and Teams clients.
Also check your registry, there are two entries under the IM provider to change the data from "Teams" to "MsTeams".
HKEY_CURRENT_USER\Software\IM Providers
- Name: DefaultIMApp
- Type: REG_SZ
- Data: Teams
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