Yahoo apologizes for Windows Phone 7 data bloat

Yahoo today offered an apology to Windows Phone 7 users affected by an inefficiency that left some with larger than usual data usage.

The data problem had cropped up shortly after the launch of Microsoft's latest mobile venture, with some users finding their allotted cellular data use going up to an unusually high rate. Microsoft acknowledged the problem in mid-January following a query from the BBC and later said that it was an unnamed third-party's fault.

Last night Microsoft fessed up that Yahoo was that third party and that the issue centered on its Web mail service. This was following a packet sniffing investigation by tech blogger Rafael Rivera, who discovered Yahoo was sending back larger than usual amounts of data every time the phone checked for new mail.

"Tens of millions of people check their Yahoo Mail from their mobile device each day, and we know they want their mobile mail experience to be fast, rich, and real-time," Yahoo said in a statement. "While our default settings on all mobile platforms realize this approach, we have determined that an inefficiency exists in the synchronization of e-mail between Windows Phone Mail clients and Yahoo Mail, which can result in larger than expected data usage for some users."

Yahoo reiterated that a fix for the problem was on the way, and will be here "in the coming weeks," but that for now users needed to dial back how often Windows Phone 7 devices check for mail updates. Yahoo also noted that the data issue was not affecting other phone platforms and apologized for any inconvenience to users.

There's no word yet on whether the fix can be made without users having to update their phone's system software.

Update at 7:22 p.m. PT: Yahoo has issued an additional statement about the issue to CNET, noting that it's not present on other mobile platforms:

Yahoo! Mail is widely available on tens of millions of mobile phones, including those running on Apple iOS, Android, Nokia Symbian, and RIM. The issue on the Windows Phones is specific to how Microsoft chose to implement IMAP for Yahoo! Mail and does not impact Yahoo! Mail on these other mobile devices. Yahoo! has offered to provide Microsoft a near-term solution for the implementation they chose, and is encouraging Microsoft to change to a standard way of integrating with Yahoo! Mail, which would result in a permanent fix.