All feedback is welcome.
The mark as (not) junk button is missing the icon. This should be done by markasjunk2 plugin. The delete and archive buttons work only if a message row is selected. This is a little bit inconsistent because all other commands work for the message row from where the right click is triggered. Either the commands should be set as inactive when no row is selected or they should work without selection. Personally I'd prefer the second option.
Great job! Thank you.