Set a relayhost for non local in master.cf

[Pedro David Marco]

Hi,
with Postfix 2.11 i am tryting to use a relayhost for non-local mail..
if i put:
relayhost = [192.168.1.10]
in main.cf, then it works ok. 

But if i put it in master.cf like this:
smtp      unix  -       -       -       -       -       smtp
        -o relayhost=[192.168.1.10]
then it does not work... why??
Thanks!