I posted my problem earlier on netbsd-users but I think it belongs here 
since this seems to be a bug with mail/postfix.
I'm not sure if RPATH should be set in option.mk or not.

>RPATH missing from binaries compiled in pkgsrc work dir?  I'd look at
>the script and see what it calls (add -x to sh?).  libtool makes
>wrappers that are supposed to link on the fly, but I don't know if
>postfix uses libtool.
>
Just as you suspected - these binaries are missing the RPATH and no 
postfix doens't use libtool.

+ bin/postconf -d -h daemon_directory
Shared object "libpq.so.3" not found
...
+ bin/postconf -d -h command_directory
Shared object "libpq.so.3" not found
...
+ bin/postconf -d -h queue_directory
Shared object "libpq.so.3" not found
...
...
...
+ test -z 1
+ echo ./postfix-install: Error: "" should be "no" or an absolute path name.
./postfix-install: Error: "" should be "no" or an absolute path name.
+ exit 1
*** Error code 1

Stop.
make: stopped in /u/netbsd/pkgsrc/mail/postfix
*** Error code 1
--
Bryan Buecking