There are several ways to reduce your mailbox size.
You can use the Mailbox Cleanup tool to view the size of your mailbox and individual folders. This tool can also help you search for older or very large messages that you might want to delete or move to an Outlook Data File (.pst).
Often, the cause of a large mailbox is a large Deleted Items folder. The tool provides a button to view the size of your Deleted Items folder and empty your Deleted Items folder.
Occasionally, Outlook will store conflicted items in a folder called Conflicts. Conflicts happen when a copy of an item stored on your email server is out of sync with a copy of an item stored on your local computer. The Mailbox Cleanup tool can delete these conflicts for you.
Run the Mailbox Cleanup tool
- Click the File tab.
- Click Tools > Mailbox Cleanup.
- Select View Mailbox Size, Find items older than, Find items larger than, View Deleted Items Size, Empty Deleted Items folder, View Conflicts Size, or Empty Conflicts to perform your desired task.
Use Conversation Clean Up to remove redundant messages
In a long email thread, there are often numerous messages that contain all of the same information as prior messages. Conversation Clean Up can remove those redundant messages automatically. For more information, see Use Conversation Clean Up to delete redundant messages.
Search for large messages
You can search for all messages larger than a specific size from Outlook's Search box. Click in the Search box and type: messagesize:>5 mb. This will find all messages larger than 5 MB. You can delete some or all of these messages or move them to another Outlook Data File (.pst). For more information on moving items, see Move or copy a message between folders.
