How to fix outlook when it's showing duplicate inbox folders

This is a known hit-or-miss issue with Outlook 2013, 2016 and 2019.

Symptoms:

• Mail isn't populating
• The Inbox, Sent Items, Outbox, Junk Email folder etc. may show up as subfolders of the Inbox folder.

Until Microsoft releases an update to fix the issue, use the following workaround:

Important: create a backup before making any changes!

Outlook 2013

1. In Outlook 2013, navigate to Home > Info > Account Settings > Account Settings:
   
2. Select the IMAP account and click Change (or double-click the IMAP account name)
3. Navigate to More Settings > Advanced and enter INBOX in the Root folder path field
4. Click OK > Next > Finish
   
   

Outlook 2016/2019

1. In Outlook 2016/2019, navigate to File > Account Settings > Account Settings.
2. Select the IMAP account and click Change (or double-click the IMAP account name)
3. Enter INBOX in the Root folder path field
   
4. Click Next > Done
   

All default folder will show up as top-level ones and mail will start populating to the Inbox folder.

Additionally, these settings can be accessed from the Windows Control Panel > Mail. If you do not see Mail, change the "View by" option from Category to Small Items. In Mail, click Email accounts, then double-click on the IMAP account, click More Settings and follow the instructions above.