Mail Outgoing blocked. Reason :Daily Mail Size Quota Exceeds Limit [Total Mail Size=512,000]

Mail Outgoing blocked. Reason :Daily Mail Size Quota Exceeds Limit [Total Mail Size=512,000]

I got this message.

Mail Outgoing blocked. Reason :Daily Mail Size Quota Exceeds Limit [Total Mail Size=512,000]

How do I unblock this account?