[Mimedefang] filter_sender activation

[Fox, Randy]

I'm trying to activate filter_sender but it doesn't seem to be getting called.  I'm using mimedefang-multiplexor with -s /var/spool/MIMEDefang/mimedefang-multiplexor.sock.  My filter looks like this:

sub filter_sender {
    my($sender, $hostip, $hostname, $helo) = @_;
    if ($sender =~ /ert\d+try\@yahoo.com/i) {
        return(0, "Mail from $sender not permitted");
    }
    return (1, "OK");
}

I've tried logging activity as filter_sender is called but nothing gets logged.  I'm using V2.28.

Thanks,
Randy