smtpd_relay_restrictions (default: permit_mynetworks, permit_sasl_authenticated, defer_unauth_destination)
Access restrictions for mail relay control that the Postfix SMTP server applies in the context of the RCPT TO command, before smtpd_recipient_restrictions. See SMTPD_ACCESS_README, section "Delayed evaluation of SMTP access restriction lists" for a discussion of evaluation context and time.