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.
- Which languages does Cortana support?
- Where can I find info about the amount of memory on my Lumia?
- How do I find the MAC address and other phone information of my Lumia phone?
- How do I open a DNG photo after transferring it to my Windows computer?
- Where are the stories stored and how can I view them later?