procmail delivery to MAILDIR

Hi,

        I have a system with sendmail and procmail 3.14
working with delivery to MAILDIR.

       When I try to delivery to MAILDIR that not exist
procamil said :

              "Unable to treat as directory /var/spool/mail/USER1"

All process of write or read is with user "mail" and the authenticate
method is lookup in /etc/poppasword file, like password but all uid
and gid map to uid and gid of user mail.

All work if I had create the user directory. The procamil work ok make
to delivery to MAILDIR method.

But when the directory don't exist said the error  "Unable to treat as 
directory /var/spool/mail/USER1"
What happend ?

Thanks in advance !