Many users try to find solutions related to fix duplicate emails in Mac Outlook when their inbox becomes cluttered. Duplicate messages usually appear because of synchronization issues. If the internet connection drops during email download, Outlook may download the same email again. Accessing the mailbox from multiple devices can also create duplicates. Email rules sometimes copy the same message into several folders. These duplicates make inbox management more difficult. Adjusting sync settings can reduce the issue. Regular cleanup keeps Outlook organized.
Get more info - https://www.vsoftware.org/blog/why-do-duplicate-emails-show-up-in-mac-outlook.html