After you’ve been running Outlook for some time, you may feel that your inbox is cluttered and could benefit from a Spring clean. Outlook’s integrated Clean Up tool removes messages from your email folders that you no longer need.
Step 1: To use it, select Home > Clean Up.
Various options are available to tidy up your messages:
Clean Up Conversation– delete redundant email messages from a selected conversation.
Clean Up Folder– delete redundant email messages from a selected folder.
Clean Up Folder & Subfolders – delete redundant email messages and conversations from Inbox and any other folders.