Yahoo! Mail data bug affecting iPhones as well as Windows Phone 7
Yahoo! blamed Microsoft for an 'unusual implementation' of IMAP on Windows Phone 7, and attempted a quick fix to correct the problem. It's unclear at the moment whether Apple also uses an unusual implementation, or whether Android, Symbian and BlackBerry users are affected too. Considering Yahoo! Mail is still the second largest webmail provider, this poses quite a potential problem for a lot of smartphone users.
Until the issue is sorted, Yahoo! Mail users on all mobile platforms are urged to watch their data usage and turn off push to prevent breaking their allowance and racking up expensive bills.