How can I run Postfix in FIPS-140 compliant mode on RHEL?

How can I run Postfix in FIPS-140 compliant mode on RHEL 6 or 7?
Is it enough to put the kernel into enforcing mode as described here https://access.redhat.com/solutions/137833, or do I need to modify Postfix too?

Or does the Red Hat Postfix distribution include the modifications to make it run in FIPS mode?

Thanks for your help,
Rob Maidment