I had the same question when I noticed repeated emails and started reading about Outlook Mac duplicate email issue. Outlook may download emails twice when there is a synchronization conflict with the server. Sometimes slow internet connections interrupt the download process. When Outlook reconnects, it may fetch the same message again. Incorrect send and receive settings can also trigger duplication. Email rules or filters may copy the same email into several folders. These duplicates create confusion while managing emails. Fixing account configuration usually helps solve the issue.