Sometimes the Mail app on your iOS device may show an incorrect unread email count when there actually aren’t any unread mail messages in your inbox.
To fix this you need to do the following.
- Go to “Settings”
- Select “Mail, Contact, Calendars”
- Select the mail account that shows the unread message.
- Turn “Mail” to “Off”
- Turn the iPhone / iPad off by holding down the power button for 5 seconds and slide to power off.
- Wait for 30 seconds, turn the iPhone / iPad back on.
- Go to “Settings”
- Select “Mail, Contact, Calendars”
- Select the respective Mail account
- Turn “Mail” back to “On”