I had similar situation for couple of days. Mail was checked continuously from IMAP push enabled account and messageserver was chewing CPU cycles like there's no tomorrow. I have nice log files of the situation. However, as last resort before filing bug I deleted and recereated the account at N9 "Account" application and the messageserver loop disappeared. If you would like to see the logs I can provide them. I can't interpret what is happening in logs. It looks like msgindexer can't turn the "pushEnabled" to "1", it keeps returnin as "0". I suspect my problem started with "Reset -> Restore settings" and then restoring from backup. I don't have the problem currently so I assume it's no use to file a bug. Let me know if you want to see the logs anyway.