Managing the quota (mailbox size) of your (Microsoft 365) account using Outlook for Windows

Your Exchange mailbox has a finite storage quota (100 GB for faculty and staff). It's good practice to monitor your quota and delete unnecessary email messages to keep your mailbox well below quota.

Check your quota

  1. From the top-left corner click File.
  2. Under Info look for Mailbox Cleanup.
    This screenshot depicts the Outlook File menu, with Cleanup Tools and Mailbox Cleanup selected. The Cleanup Tools button is located beneath the Automatic Replies button. The Mailbox Cleanup button is the first option in the drop-down menu that appears after clicking on Cleanup Tools.

Reduce the size of your mailbox

  1. Click Tools > Mailbox Cleanup.
  2. Use the Find... feature to search for old or large messages. Delete any unneeded messages.
  3. Select AutoArchive to move old items off of your Exchange account and onto your computer's local storage.
  4. Empty your Deleted Items folder to permanently remove deleted items from your mailbox.
  5. Delete alternate versions of items to remove duplicate messages.

For additional assistance please contact the IT Support Center at 847-491-4357 (1-HELP) or via email at

Keywords:outlook email mail account space data storage full Exchange O365 M365   Doc ID:62238
Owner:TSS Tier 2 .Group:Northwestern
Created:2016-03-25 22:22 CDTUpdated:2020-12-14 12:19 CDT
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