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 do I remove an account from my Lumia phone?
- How do I insert dialing pause into a contact phone number on my Lumia phone?
- What is the glance screen for my Lumia phone?
- Where can I find information about WhatsApp, Skype, Angry Birds, Twitter, NimBuzz, Viber, Fring, or some other non-Microsoft application (3rd party application)?
- What are effects on the Cinemagraph app on my Lumia phone?