1. Open Outlooks desktop application.
2. Select File >Info >Cleanup Tools>Mailbox Cleanup.
3. Under Mailbox Cleanup, start by seeing where all your space is being used. Select the View Mailbox Size… button. Then select the Server Data tab. Here you can see how much data is in each folder and your calendar. For your reference, 1024 KB = 1MB.
4. Now search for emails that are taking up most of your space. To do this, close the Folder Size window. Then, select your preference of old or large items. Finally, select the date or size you would like to search for and select Find…
5. A window will now appear with the results of your search. If you would like to delete all these messages, single click on a message, then press Ctrl+A to select all the messages, then press delete. To delete a block of messages, single click the first message you want to remove, then Shift + single click on the last message, then press delete.
6. Now go back To Mailbox Cleanup. Select the Delete button next to “Delete all alternate versions of items in your mailbox.”
7. Return to Mailbox Cleanup and select Empty next to “Emptying the deleted items folder permanently deletesthose items.”
8. Finally, return to Mailbox Cleanup and see how much space you have freed up.
9. Select the “View Mailbox Size…” button. Then select the “ServerData” tab.
