The mailbox may have some emails with an excessively long subject line that are not supported by Windows Phone 8. Once you have removed the suspect mail item (i.e. cleaned the mailbox or move the suspect mail to a folder that phone does not sync) the error will cease.
- I am not receiving audio when playing music or games on my Lumia phone
- My Lumia's battery does not get fully charged
- What can I do if the camera on my Lumia phone does not work properly?
- I cannot send or receive text messages on my Lumia phone
- I cannot send or receive multimedia messages on my Lumia phone