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.
- Why do I see 'Critical update' notification on my Lumia phone?
- Where are the stories stored and how can I view them later?
- What is the difference between public and private sharing in the Storyteller app?
- Can I delete stories that I have shared with the Storyteller app?
- How can I share my story in the Lumia Storyteller app?