[imp] over quota and can't delete mail

[php at gurubase.com]

Dear all,

I cannot delete the mail when I am already overquota. By default, I will move the 
deleted mail to Trash but when I am overquota, this operation is not allowed. 

I am using IMP 3.1 , Cyrus, Postfix

Are there any ways I can work around it? 

Thanks and regards,
Boris