Mail App Showing As "talagent" in Mission Control
From a wild guess in comments, which seems to have worked…
talagent is the service responsible for relaunching apps after a restart etc.
Something has got confused, so try…
Quit Mail, then delete the contents of
~/Library/Saved Application State/com.apple.mail.savedState/
(not the folder itself as it's an alias) Then relaunch Mail.