The issue, which was first picked up by users at the beginning of the year, lets Windows Phone 7 devices send and receive data without their owner's knowledge, resulting in unusually high data bills for some of them.

 

Initially Microsoft refused to name the responsible party, but now according to ZDNet the company has finally released a statement placing the blame squarely on Yahoo.

 

The statement read, “We have determined that an inefficiency exists in the synchronization of email between the Windows Phone Mail client and Yahoo! Mail. This inefficiency can result in larger than expected data usage for a very small percentage of users. Microsoft and Yahoo! have worked together to identify a fix, which will be rolled out in the coming weeks.”

 

The error apparently exists in a piece of code that tells Windows Phone 7 how to fetch new email messages from Yahoo! Mail. The error results in the system downloading up to 25 times as much information as it needs to.

 

No word on how Microsoft is planning to deal with undoubtedly disgruntled users at this stage, but let's hope it's not going to be a recurring issue on the company's new mobile OS.