fatal: parameter “smtpd_recipient_restrictions (POSTFIX)

maillog error message

fatal: parameter “smtpd_recipient_restrictions”: specify at least one working instance of: check_relay_domains, reject_unauth_destination, reject, defer or defer_if_permit.

Like the error message states: we need to add one of the followings in the smtpd_recipient_restriction section:
check_relay_domains, reject_unauth_destination, reject, defer or defer_if_permit.

Just add it. See my smtpd_recipient_restrictions below

smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination

Make sure you restart your POSTFIX server