Perhaps many of you did not know, but some users of Windows Phone 7 terminals complained that their devices were making unauthorized data traffic. Microsoft investigated the problem and finally discovered that Yahoo! is to blame for this problem. It looks like Yahoo's IMAP mail servers reference users much more data than the dedicated e-mail applications required, the result being a very high traffic for some simple checks of an e-mail. Microsoft and Yahoo blamed each other until it was discovered that this problem also affects users of iPhone terminals, but not those of Android terminals.
Maybe Yahoo should have done their homework a little bit more before accusing Microsoft for the data leakage problems on Windows Phone 7. Upon reading the accusations, Rafael Rivera took it upon himself to prove that it did occur on other platforms, the iPhone in this case . and answer he did. He ran a similar test with the help of a friend's iPhone and got a similar result whereby the Yahoo servers returned more data than requested. The whole process is quite technical, so head over to his site to read the entire process.
In practice, the mail application requests certain information from Apple's servers, in a "simple" format for mobile phones, but Apple's servers send much more data that normally should not be sent. In this way, additional traffic is generated that sometimes unjustifiably charges users' bills. For now Yahoo! it does not recognize the problem and has not solved it, and for the iPhone there is no method to prevent this excess traffic. In order for this problem to affect you, you must have a Yahoo! account set up in the iOS Mail application.
