Below is a list of steps to troubleshoot the issue of emails being duplicated in your inbox.

1. Check all folder locations, tagging settings, and rules to make sure no automated actions are configured
2. Check whether forwarding settings are enabled in any account management settings
3. Check the email setup parameters in the email client application to ensure no duplicate copies have been configured during original setup
4. Check the email storage limit in the respective email accounts to see if this copies of emails are expiring due to the full storage