Sending only local mail to another mail server

[Martin Brampton]

I'm running a Postfix server that receives mail for a number of domains, 
and provides service for mail users via Dovecot. It's not used for 
sending mail from users, another server acts as the mail relay.

Is it possible to configure my Postfix server so that locally generated 
mail (e.g. from cron jobs) is sent to the other server rather than being 
delivered locally? If so, how would this be achieved? (I want to achieve 
a consistent path for all mail that reaches accounts).