One bug that I have faced 3-4 times in Gmail app with Hotmail is that after I delete an email received, Gmail pulls the same message & displays as a new mail again & again. So, I left it & deleted after few minutes.
I guess the delete doesnt get updated in Hotmail & Gmail no longer finding in inbox keeps pulling it. First I thought that the sender had automated email issues & was repeatedly sending messages , but found there was only one when logged in via website. Since then it was happened atleast 2 more times that I can remember.