Step 1: To clean up your inbox, first make sure that you select your inbox which is located in the folder pane on the left hand side.
Step 2: Then you much go to the Ribbon Pane > Home > Delete Group. From there, click the Clean Up button.
Step 3: There you will see three options; Clean up conversation, for if you want to clean up a single selected conversation, Clean up folder, if you want to clean up every conversation in the selected folder, and lastly Clean up folders and Subfolders for if you want to clean both of them out.
Step 4: Once you select your option, a dialogue box will appear indicating that your deleted items will be moved into the Deleted items folder.
Step 5: If you wish you have your deleted items moved into a different folder, select settings, which will open up another dialogue box. From there, scroll down until you see the title box Conversation Clean up. Then you will browse to see which folder you want your items to be placed in. Once satisfied with your changes, click OK.
Step 6: Once you click OK, another dialogue box will appear. Select Clean Up Folder. This demand will then clean up the conversations that you selected.