Testing MailExtension in Mail out of Xcode

Hello,

I am playing around with MailKit in Xcode... just created a new App with MailExtension target. When I run it, it's asking if I want to test it with Mail, however, I cannot see the extension in the Mail Settings for enabling it...

I a totally newbie here.... what am I missing?

Testing MailExtension in Mail out of Xcode
 
 
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