I have noticed that when my network connectivity is poor, Airmail does some strange things. Snoozed emails for "later" pop back within minutes. Emails I write and send don't go out in the background, so I had a case where I wrote an email whilst having poor (but not zero) network connectivity and Airmail only tried to send it when I opened the app again the next morning. I'd like to know when something is stuck in my outbox.