"Outlook Email Stuck in Outbox" refers to a common issue where an email remains in the Outbox folder and cannot be sent. This can occur due to various reasons including a slow internet connection, large attachments, or conflicts with antivirus software. To resolve this issue, it's recommended to check network connectivity, delete large attachments, and temporarily disable antivirus software. If these steps don't work, restarting Outlook may help resolve the issue.