Earlier in April we heard reports of high data consumption on some Windows Phone 7 devices. As I said, after using Windows Phone 7 devices since last July I have seen no abnormal data usage so thought it had to be a rogue app, either a 3rd party one or a carrier branded one. Paul Thurrott just posted that Rafael, from the Within Windows site, discovered that Yahoo! Mail was consuming an abnormal amount of data and then Microsoft just confirmed they figured this out too. They didn't say why they did not share this with us earlier, but they are apparently working on a fix.
I don't use Yahoo! Mail so that might explain why I haven't seen any abnormal data consumption. Microsoft has also identified some issues with email sent via Exchange ActiveSync that a select few people have experienced. I have a work Exchange account and two Gmail accounts setup through EAS and haven't experienced any issues at all. Actually, email is fantastic on Windows Phone 7 and I prefer to use my HD7 rather than Outlook and the web browser on my PC.
Any readers with WP7 and Yahoo! Mail setup seeing higher than normal data consumption?