TRY ADDING RBLS TO CHECK MAILS WITH BLACKLIST
HERE FIND THE USE CODE AND UPDATE IN POSTFIX MAIN.CNF FILE
smtpd_recipient_restrictions = permit_sasl_authenticated,
permit_mynetworks,
check_client_access hash:/etc/postfix/sender_whitelist,
check_client_access hash:/etc/postfix/sender_blacklist,
reject_unauth_destination,
reject_non_fqdn_sender,reject_unknown_sender_domain,
check_sender_access hash:/etc/postfix/access,
reject_non_fqdn_recipient,
reject_unknown_recipient_domain,
reject_rbl_client zen.spamhaus.org,
reject_rbl_client bl.spamcop.net,
reject_rbl_client dnsbl.sorbs.net,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client b.barracudacentral.org,
reject_rbl_client dnsbl-1.uceprotect.net,
reject_rbl_client noptr.spamrats.com,
reject_rbl_client dyna.spamrats.com,
reject_rbl_client spam.spamrats.com,
reject_rbl_client dnsbl.inps.de,
reject_rbl_client combined.abuse.ch,
reject_rbl_client bl.blocklist.de,
reject_rbl_client dnsbl.darklist.de,
reject_rbl_client dnsrbl.org,
reject_rbl_client spamlist.or.kr,
reject_rbl_client dnsbl.openresolvers.org,
reject_rbl_client dnsbl-2.uceprotect.net,
reject_rbl_client dnsbl-3.uceprotect.net,
reject_rbl_client blacklist.woody.ch,
reject_rbl_client xbl.spamhaus.org,
reject_rbl_client sbl.spamhaus.org,
reject_rbl_client pbl.spamhaus.org,
reject_rbl_client misc.dnsbl.sorbs.net,
reject_rbl_client zombie.dnsbl.sorbs.net,
reject_rbl_client smtp.dnsbl.sorbs.net,
reject_rbl_client socks.dnsbl.sorbs.net,
reject_rbl_client spam.dnsbl.sorbs.net,
reject_rbl_client http.dnsbl.sorbs.net,