How to Clean Up and Reduce Your Mailbox Size

1. Mailbox Cleanup

The best place to start is to open the Mailbox Cleanup tool. In Outlook, choose File > Info > Cleanup Tools > Mailbox Cleanup.

1. First, choose the View Mailbox Size option which scans the size of your mailbox and all of the subfolders. This is a great way to target which folders are the biggest contributors to your large mailbox so you can clean these up first.
   When connecting to Exchange, you’ll see a Local Data and Server Data tab. Only look at the Local Data tab; cleanup changes you make will automatically take place on the server as well.
2. Next, pick the options to Find older or larger items which you can delete directly from the results to cleanup the Outlook mailbox size.
3. Depending on your archive settings (see Archive Older Messages below), you can also run an AutoArchive.
4. Finally, check the size of the Deleted Items folder and Empty the folder if you want (specific options detailed below as well). If available, one option is to view and delete multiple versions of items in our mailbox.

2. Archive Older Messages

Another useful maintenance step is to periodically archive your Outlook folders. If you are accessing Outlook from Exchange, you may not be able to change archive options as archiving is often controlled by system administrators or a third party program.

Setup your archive preferences under the Info > Cleanup Tools > Archive option. The archive.pst file can be created and updated at any location you specify, usually your local hard drive. Archived items are removed from your Outlook mailbox size and moved to the archive file based on the settings you determine. Just as with the Personal Folders file, your archived items are not accessible remotely; the file should be backed up on a regular basis.

3. Empty Deleted Items

Quickly clean up your deleted items by automatically emptying the Deleted Items folder when you exit Outlook. To apply this option choose File > Options > Advanced tab. From the Outlook start and exit option, check Empty Deleted Items folder when exiting Outlook and OK to apply.

To manually clear deleted items, locate and right-click the Deleted Items folder and click Empty Folder on the shortcut menu (Empty “Deleted Items” Folder for Outlook 2010). Once you clear deleted items, it cannot be reversed. If you feel confident that you want to delete a message forever, you can bypass the Deleted Items folder by pressing [Shift] + [Delete] for a selected item instead of pressing the [Delete] key. Then confirm the delete process.

4. Save and Remove Attachments

Attachments in email messages are responsible for a bulk of the space used in your Outlook mailbox. Depending on the email communication, one option is to save the attachment and then to remove the attachment from the original message. This requires extra steps yet may help slim down the size of your Outlook mailbox:

1. Open the message.
2. Right-click on the attachment and then pick Save All Attachments. Or select Actions from the Message tab. Then pick Other Actions > Save All Attachments.
3. Next, locate and select the folder where you want to save the file(s) and pick Save.
4. Once you have saved the attachment, delete the message if it doesn’t need to be retained. If you need to keep the message, you can remove attachments from a message by right-clicking them and choosing Remove.