If Outlook is filling up with duplicate emails, the easiest way to remove them is by using a dedicated duplicate remover tool. You can try manual methods like sorting emails by date/subject and deleting duplicates or using "Clean Up" in Outlook, but they don’t always catch everything.
For a reliable, automatic solution, SysTools Outlook Duplicate Remover is great. It scans your PST/OST files and removes duplicate emails, contacts, calendars, etc., without affecting original data. You can also compare items across folders and apply filters for specific dates, making cleanup fast and accurate.