[Exim] Mail Quota's & NON-DEFERING

I was looking over the dox trying to see how to impose quotas. I saw the
QUOTA= paramater, but when I experimented with that, It didn't work right.
It defered the mail. I don't want the mail sitting for four days then being
bounced back. I wanted to implement a one check system. If the user's
mailbox is full, then abort delivery and return an error.

I'll keep looking, but does anyone know how to set that?