- Open Outlook, and click on the Search textbox in the top right-hand corner.
- On the left-hand side, click on All Mailboxes.
- Click on Advanced.
- Click the drop-down list labeled Item Contains, and click on Size.
- Click on the drop-down list next to Size, and select Is Greater Than. In the textbox, type in 150000.
- If any emails are found, move them to your archive folder.