From Outlook Web Access
1. Select the gear icon in the upper right-hand corner of the page and select "Options."

2. Select "General" to expand it and then select "My account."

3. You can view how much space is remaining under Mailbox usage.

From Outlook for Windows
1. Select the "File" tab in the ribbon.

2. If it isn't already open, select "Info."

3. You can view how much space is left under Mailbox Cleanup.
