Hi,My postfix server was rejecting emails from the following server. I think it is because I am using "reject_unknown_helo_hostname".
------------------ start ------------------Nov 15 13:20:13 mail postfix/smtpd[14663]: NOQUEUE: reject: RCPT from unknown[103.230.232.100]: 450 4.7.1 <DD1HMALPPPPT02.hmail.sg>: Helo command rejected: Host not found; from=<fromname@fromdomain> to=<toname@todomain> proto=ESMTP helo=<DD1HMALPPPPT02.hmail.sg>
------------------ end --------------------From the helo, I can see DD1HMALPPPPT02.hmail.sg. But this domain does not resolve, as you can see bellow. So comes my question, is it complulsory for an outgoing smtp server to have a fully qualified domain name. With an "A" record.
If it is not complusory then my setting was too strong and I really should remove "reject_unknown_helo_hostname".
Need advice. -------------- start ----------------- dig DD1HMALPPPPT02.hmail.sg ; <<>> DiG 9.9.4-RedHat-9.9.4-51.el7 <<>> DD1HMALPPPPT02.hmail.sg ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 9803 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 512 ;; QUESTION SECTION: ;DD1HMALPPPPT02.hmail.sg. IN A ;; AUTHORITY SECTION: hmail.sg. 899 IN SOA pridns.hmail.sg. hostmaster. 205 900 600 86400 900 ;; Query time: 14 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Wed Nov 15 23:43:43 +08 2017 ;; MSG SIZE rcvd: 105 --------------- end ------------------ -- P.V.Anthony
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Description: S/MIME Cryptographic Signature
