Posted PlainNote for review two days ago and got the rejection notice last night. I used an action button to spawn the mail view and this was against user interface guidelines.
Just a quick swap to a text label and resubmitted it. For future reference if your trying to do something that isn’t an action button don’t use this:
Or map a custom image to your button which is also possible. Hopefully in a couple more days it will be available. I’m encouraged by how fast it got reviewed though that was only about 48 hours vs my previous submissions taking over two weeks.