For years I used Maildroid email app. Loved it. Still wish it had better Tizen support because it was lightning fast vs other email apps and the developer actually responded and cared about constantly improving it. But then I tried Samsung's stock email app, and while it was okay, I was shocked at how it and Samsung's own "messages" app wasn't optimized for their own watch. With Samsung Messages, group texts didn't work. They didn't come up on the Gear S3 as a group message and when you replied, you only could reply to the single individual that wrote the message you were replying to, not the group. Huh? With the email app, it didn't show the whole message on the watch. Only the sender and subject. Sadly Maildroid was the same. So I tried a few more and fell upon Blue Mail and while it's not perfect, it's very full featured and emails show a lot of the body of the message. Now I do wish you could see which email account each email was going to either by name or by color or something on the watch, but I'll live with it and hope the implement that soon. Long story long...I just sent a test email to myself and deleted it and it did delete on my phone too. This was using the Blue Mail app, not the stock email app. Maybe someone else knows a way but I figured I'd try it and report using what I use.