postmap /etc/postfix/whitelist_domains

vi /etc/postfix/main.cf

smtpd_recipient_restrictions =
reject_invalid_hostname,
reject_unknown_recipient_domain,
reject_unauth_pipelining,
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination,
check_client_access hash:/etc/postfix/whitelist_domains,
reject_rbl_client dsn.rfc-ignorant.org,
reject_rbl_client dul.dnsbl.sorbs.net,
reject_rbl_client list.dsbl.org,
reject_rbl_client sbl-xbl.spamhaus.org,
reject_rbl_client bl.spamcop.net,
reject_rbl_client dnsbl.sorbs.net,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client ix.dnsbl.manitu.net,
reject_rbl_client combined.rbl.msrbl.net,
reject_rbl_client rabl.nuclearelephant.com,
permit

service postfix restart

● postfix.service - Postfix Mail Transport Agent
Loaded: loaded (/usr/lib/systemd/system/postfix.service; enabled; vendor preset: disabled)
Active: active (running) since Tr 2018-08-29 18:32:05 CEST; 1s ago
Process: 10656 ExecStop=/usr/sbin/postfix stop (code=exited, status=0/SUCCESS)
Process: 10672 ExecStart=/usr/sbin/postfix start (code=exited, status=0/SUCCESS)
Process: 10669 ExecStartPre=/usr/libexec/postfix/chroot-update (code=exited, status=0/SUCCESS)
Process: 10666 ExecStartPre=/usr/libexec/postfix/aliasesdb (code=exited, status=0/SUCCESS)
Main PID: 10748 (master)
CGroup: /system.slice/postfix.service
├─10748 /usr/libexec/postfix/master -w
├─10750 pickup -l -t unix -u
└─10751 qmgr -l -t unix -