allow databytes based on username with qmail-ldap

Hi All

I have configured qmail-ldap its working fine, I have allowed some specific user to send a big attachment using tcp.smtp but its IP based.

I know I can make the control based on IP, through the variable DATABYTES .rules in SMTP, but this does not working for me, since basically work with DHCP. 

I goggled & found this "http://marc.info/?l=qmail&m=111384336315694&w=2" but its not working.

does anyone know if there is something like this?

Any advise greatly appreciated.

Thanks & Regards
Jadav Dilip