Can a MailKit MEMessageActionHandler process all incoming messages?

As best as I can tell, the only messages sent to a MEMessageActionHandler for processing are those going to the Inbox. I'm trying to write a Mail extension that processes incoming messages, most importantly those that go straight to the Junk folder, but none of those messages go to the extension.

Is there some setting I may be missing or can a MEMessageActionHandler only process emails going to the Inbox?

Tried the same, did not handle the messages downloaded to the folders outside of the Inbox. :(

Can a MailKit MEMessageActionHandler process all incoming messages?
 
 
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