usrquota()
  Check user quota for an recipient.
  
  This scanner can be used to check user quota for an recipient.
  It only can raise an error, if quota is exceeded, or it can return
  clean. This scanner is only valid in combination with lmtpd() service.
  
  Usage: usrquota(mydestination)
  
  Where: mydestination is an regular expression, which defines local domains.
           If it is set and only one recipient is specified
           and recipients domain matches against this regular expression,
           then username part will be sent into spamd.
  
  Example: usrquota('mydomain.sk')