I am using Android Outlook and had same issue with one of the folder having clock icon next to the name and emails appearing under Scheduled folder.
Almost tried everything posted here.
Finally, MFCMAPI solved the issue.
- Uninstall the App from Mobile.
- Try downloading MFCMAPI on the desktop for Outlook version you are using.
https://github.com/stephenegriffin/mfcmapi/releases/tag/17.0.17099.01
- Find and delet the affected folder using following guides:
http://o365info.com/delete-corrupted-hidden-exchange-inbox-rules-using-mfcmapi/
https://www.howto-outlook.com/howto/hidemovedeletemfcmapi.htm
- Re-install Outlook Mobile App, login and check the Folder :)
This worked for me.