After users began noticing that their Windows Phone 7 devices were pulling down more data than they could account for, the search began for a possible culprit. After a handful of apps were suggested as potential sources for the excess data, traffic analysis finally nailed Yahoo Mail as the service at the root of the problem. Most of this played out weeks ago, and there hasn’t been much in the way of updates since the beginning of February. Now it looks like Yahoo has finally taken steps to alter the behavior of its servers, no longer sending WP7 phones this extra data.

Problem was, Yahoo Mail wasn’t properly responding to the periodic requests for mailbox updates which WP7 smartphone would send out. The devices would request only a small subset of available data, just enough to learn about new mail, only for Yahoo to send a lengthy block of text containing full message headers. While a small amount of data individually, combine this with frequent mailbox checks and plenty of e-mails, and you have the recipe for a lot of wasted data.

While Yahoo hasn’t yet announced that it’s implemented a fix, Rafael Rivera has been monitoring the state of Yahoo’s servers, and found today that the system reports a new version of the IMAP software it uses, as well as confirmed the fix by querying the server with a request that would have previously triggered the problem.

Now we’ll just have to wait and see if WP7 users (at least those who haven’t followed Microsoft’s advice to limit the problem’s impact) report lower monthly data usage.

Source: Within Windows

Via: Windows Phone Secrets