What is wrong with these pf rules?

[Leon Botes]

binat on $dig_if from $dmz_srv to any -> $dig_ip2
binat on $dsl1_if from $dmz_srv to any -> $dsl1_ip2
binat on $dsl2_if from $dmz_srv to any -> $dsl2_ip2
rdr on $dig_if inet proto tcp from any to $dig_ip2 port { 25, 80, 81, 
110 } -> $dmz_srv
rdr on $dsl1_if inet proto tcp from any to $dsl1_ip2 port { 25, 80, 110 
} -> $dmz_srv
rdr on $dsl2_if inet proto tcp from any to $dsl2_ip2 port { 25, 80, 110 
} -> $dmz_srv

$dig_if, $dsl1_if, dsl2_if are all connected to the net via routers.
The rule works for whichever interface the default route points to.
How can i get pf to return incoming connections out the same interface 
they arrived on?

-- 
Regards
Leon