Although I'm a big fan of adding a feature to allow people to tell this transport to select `UNSEEN` messages as well as `ALL`, it doesn't look like this functionality is in use currently.  Could I convince you into removing this for the purposes of making this PR as minimal as possible.  I'm definitely +1 on approving this kind of a feature in a separate code review, though.

Again -- definitely would :heart: to help you with this (i'm fully aware of how annoying it is to receive a million code review comments, and I do apologize).