Microsoft' on Tuesday announced it had found the cause of unexpected data use on some Windows Phone 7 handsets using Yahoo Mail. But last night, Yahoo announced, in effect, "Don't blame us: it's Microsoft's fault."
Neither company has been willing to explain exactly what's causing the unexpected and in some cases extreme data usage as the handsets sync with Yahoo Mail. In a brief statement yesterday, Microsoft said it was caused by a synchronization inefficiency between the Windows Phone mail client and Yahoo Mail.
But the folks at Yahoo apparently thought Microsoft's wording implied that the mail service was to blame. Now Yahoo says that the cause is the method Microsoft chose to implement the Internet Message Access Protocol (IMAP), which is used to retrieve and send e-mail from a server. In its statement, Yahoo didn't explain how or why the implementation is problematic, except to imply that it is somehow non-standard.
This is the full statement from Yahoo:
"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."
Microsoft yesterday said that "Microsoft and Yahoo! have worked together to identify a fix." Yahoo's statement suggests most of that work has been and continues to be Microsoft's responsibility. And Microsoft's original statement doesn't indicate whether it plans to adopt a more standard implementation for integrating with the mail service.
Neither Microsoft nor Yahoo has yet replied to an e-mail asking for additional details.