The amount of email and attachments that you have stored on the email server are subject to a quota amount. Students have 10 GB of quota while faculty/staff have 500 MB of quota. Messages (to include messages that you have sent) and attachments contribute to your quota size. The maximum size for a single email message (for both sending and receiving) is 20 MB.
Check Your Quota
To check your quota status in Outlook Web Access (OWA), simply point to your name displayed at the top of the folder list.
Blocked Email Extensions