Thank You for Your time and answer, Sahil: > Show relevant logging. If it is indeed amavisd-new where the mail is > rejected (or quarantined for having spammy qualities)
I will bring here the logging for the site but from another server, just to show who and which error detected in case if it may help here for mine server: mail.log:May 6 01:57:58 myhost postfix/smtpd[10086]: NOQUEUE: reject: RCPT from unknown[3.4.5.6]: 450 4.7.1 Client host rejected: cannot find your hostname, [3.4.5.6]; from=<ag...@problemhost.net> to=<r...@myhost.org> proto=ESMTP helo=<quitewell.problemhost.net> So, this situation I try to solve by inserting the IP of problemhost.net to my whitelist in main.cf: smtpd_client_restrictions = check_client_access hash:/etc/postfix/whitelist, check_client_access hash:/etc/postfix/blacklist
