With the webpage gmail (and probably the gmail app), it will tell you that you cannot send attachment over 25Mb. With the stock email app, it does not. It will put it on the outbox and attempt to send it. It will actually try and when it reaches 25mb, it will fail. And then it will try again! And again.. and again! Well all it does is kill your battery fast if you are in the house with WiFi... now if you decided to go out... it will now eat into your 4G bandwidth (unless you are unlimited). The thing is even if you notice it, it is not easy to delete the outbox email. You cannot delete it until you put the phone on airplane mode. When it is busy sending, it won't let you delete the outbox email. I think I ran the battery down 10% before I figured out how to remove that.