If you own an Android phone, you might be experiencing the really annoying thing where emails you get that were sent from some iPhones arrive in duplicate. It is a known problem. There is no known solution. Apple knows about it but seems not to care (remember, its customers are on the sending side not the receiving side (which is not to accuse Apple of building this in to retaliate against Android phones, although Apple is well known for such engaging in such untoward tactics). One reason it is so difficult to figure out a cure is that it does not happen with all iPhones. The only solution for now is to live with it or blacklist any email address you are experiencing the problem with. If you choose the blacklist route, you might put on an auto-response that reads: "Because of your iPhone, every email you send to me arrives in duplicate. I'm mad as Hell, and I'm not going to take this any more. I've blacklisted your email address until you switch to an Android phone." You can learn the right delivery tone by watching this link: Link to Learn How to Say I'm Mad as Hell Etc.