Juniper Transparent Mode DHCP Relay

JUNOS 12.2

set security policies from-zone untrust to-zone trust policy rrdhcp match source-address router1
set security policies from-zone untrust to-zone trust policy rrdhcp match destination-address any
set security policies from-zone untrust to-zone trust policy rrdhcp match application junos-udp-any
 

Please note:  delete all the dhcp relay setting  (this is not used in transparent mode)

delete forwarding-options