A few weeks ago, I mentioned that there were reports of some Windows Phone 7 handsets having an issue where the customer’s bandwidth allowance was being eaten up by some app that was outside of their control. Paul Thurrot has posted a story with the cause of the leak: “an inefficiency exists in the synchronization of email between the Windows Phone Mail client and Yahoo! Mail”. Oh yeah, Exchange ActiveSync can also cause issues. Visit Paul’s site for more details and a workaround for the Yahoo! issue.