Yahoo! has blamed Microsoft software design for the phantom data use that occurs on Windows Phones.  

Recent reports have suggested that Windows 7 Phones connected to Yahoo!'s mail servers are transmitting twenty-five times as much information as necessary. This has major consequences for users with tiered mobile service plans, which charge fees if users go over their monthly limits.

Yahoo! released a statement yesterday, apologizing for what they called inefficiency in the way Windows phones and Yahoo! Mail interact.

Shifting the tone, Yahoo! released a second statement today. Noting the numbers of non-Windows Phones that use Yahoo! Mail with no problems, the statement says that the cause of the problem lies not with Yahoo! but with Microsoft:

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.

Microsoft plans to release a software patch for the problem in the coming days. 


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