Hi @Network Administrator (NCSS02) ,
Welcome to our forum!
As i know, the default Group Policy templates for Microsoft Outlook do not include a setting to configure the default email client. Please refer to this article and try the solution:
Cannot configure the default email client using Group Policy
(Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.)
Hope the above help!
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