domain problem haunting me

I keep getting send failures to a specific domain on my system. I get  R20;This domains mailbox's are full”;. Well, they did hit their quota which caused problems, and we had to empty out some of their backlogged email and delete some old users that were still getting billions in spam every day. They are well below their quota now. I have restarted SurgeMail, reset the quota by command line (per the manual), and all mail is still getting rejected. Is there any database cleanup utility or a re-index command that will purge this stuff out? Any ideas anyone? 

Thanks in advance.

Nick