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.
- How long does it take to start up the phone for the first time?
- What can I do to free up the phone memory on my Lumia?
- What are the known limitations with App Social Beta for Lumia phone?
- What is the Nokia Care application on my Nokia Lumia with Windows Phone 8?
- What can I do with the Nokia Care application on my Nokia Lumia with Windows Phone 8?