My OWA mail box full

My OWA mailbox is full.
I can't send or receive either. 
How can i do for this problem??? and 
I use MS outlook application also. 

Before this error, i send/receive all email from OWA by MS outlook application.
When i done this, mailbox size is fine again. I think email is moved to MS outlook application.
Now it's not fine. It's just copy to MS Outlook.
When I delete email from OWA, it's also delete in MS outlook.
I'm just beginner of Exchange Server. 
Please suggest how to solve this problem?
I'm using Exchange Server 2010.

#shinminsymon