When Yahoo has launched implementation of IMAP for Windows Phone 7, it was quickly noted that there were issues with bandwidth . A lot more data was being transmitted than actually was needed which in turn, caused a lot of users monthly allowances to be used up.Windows blog has now noticed that Yahoo! has updated the software that is responsible for collecting email via IMAP and found that the version has gone from 0.7.65_12.286037 to 0.7.65_14.298026. This newer version fixes the problem.
The exact fix is unknown, but when testing it was found that the fetch command only got a small reply back showing just the essential information, rather than the full header like before.
So go to Settings -> E-mail accounts -> Yahoo Mail -> Settings -> Download new content: “Manually” & Download email from: “The last 7 days” and you’ll notice that things will get better for you. Thurrott says that Microsoft is working on a fix which will be released in “the coming weeks.”
Well, this is how to fix the Windows Phone 7 phantom data bug until Microsoft releases the WP7 update or an official minor update which contains the fix of this bug.For those who use IMAP on Windows Phone 7, the fix is now already in place and you should see your data usage drop.