# Call as:

def blah(domain, mailbox):
    blah.isSenderDenied(domain, mailbox)\
        .addCallback(_cbSomeReply)

def _cbSomeReply(denied):
    pass



    def isSenderDenied(self, domain, mailbox):
        if not self.deniedSendersLoaded:
            return self.reloadDeniedSenders()\
                .addCallback(self._cbIsSenderDenied, domain, mailbox)

        return defer.succeed(self._cbIsSenderDenied(None, domain, mailbox))


    def _cbIsSenderDenied(self, lastResult, domain, mailbox):
        deniedSenders = self._deniedSenders

        if domain in deniedSenders:
            for expr, (source, reason) in deniedSenders[domain].iteritems():
                if fnmatch.fnmatch(mailbox, expr):
                    return source, reason