Further to the idea
It would be very helpful to have a swipe action for snoozing a message. If i do not have the time to read it, but it is important and It has to be taken care of, I could snooze it and set it at a later time. This could be "after x hours" or at a certain date and time
Marking emails as unread or flagging them never worked for me. I always end up with emails accidentally touched and marked as read but actually never read or with flagged/starred emails whose contents is either not an issue anymore or I did not take any action on time and it is too late now.