Zimbra Tips : How To Enable PTR/Reverse DNS Lookup for Incoming Email

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Most of spam email sent from public IP who did not have PTR/Reverse DNS. What is PTR/Reverse DNS, you can find more information from Wikipedia 😀 : https://en.wikipedia.org/wiki/Reverse_DNS_lookup

If you have Zimbra and want to enable PTR/Reverse DNS lookup for incoming, you can perform the following command

su - zimbra
zmprov mcf +zimbraMtaRestriction "reject_unknown_client_hostname"

Please wait few minutes until Zimbra Postfix reload. Or you can also reloading Postfix manually 😉

Good luck and hopefully useful 🙂

9 comments

  1. Hi Iman,

    i enabled DNS check but i want to receive email from server which does not configure reverse DNS. How can i do that ?

    thanks

      1. Hi Mas Iman ,
        saya sudah coba membaca link wiki di atas , saya untuk penerapan di zimbra 8.7.11 , bagaimana untuk membuat exception untuk ip yang di reject karena reverse domain nya unknown tapi kita tau itu email yang valid cuman belum di konfigurasi dengan baik .. , terimakash bnyak sebelum nya mas

          1. terimaksih banyak mas iman atas advice nya , sudah saya coba terapkan , *berikut list konfigurasi saya:
            zimbra@mail:~$ zmprov gacf | grep zimbraMtaRestriction
            zimbraMtaRestriction: check_policy_service inet:127.0.0.1:10031
            zimbraMtaRestriction: reject_invalid_helo_hostname
            zimbraMtaRestriction: reject_non_fqdn_sender
            zimbraMtaRestriction: reject_unknown_client_hostname
            zimbraMtaRestriction: reject_rbl_client b.barracudacentral.org
            zimbraMtaRestriction: reject_rbl_client zen.spamhaus.org
            zimbraMtaRestriction: reject_rbl_client psbl.surriel.com
            zimbraMtaRestriction: reject_rbl_client cbl.abuseat.org
            zimbraMtaRestriction: reject_rbl_client bl.spamcop.net
            zimbraMtaRestriction: reject_rhsbl_client dbl.spamhaus.org
            zimbraMtaRestriction: reject_rhsbl_client multi.surbl.org
            zimbraMtaRestriction: check_client_access lmdb:/opt/zimbra/conf/postfix_rbl_override
            *list exception di file postfix_rbl_override :
            #ip email pajak.go.id
            103.28.106.55 OK
            103.28.106.91 OK
            103.28.106.9 OK
            103.28.106.152 OK
            103.28.106.90 OK
            103.28.106.151 OK
            SVR-EXCH-DEV-01.intranetdev.pajak.go.id OK
            tapi masih ada ip atau domain yang saya masukan di rbl_override masih ke reject , mohon saran nya , terimakaish banyak sebelum nya mas iman
            *log email yang di reject
            Mar 12 08:16:34 mail postfix/smtpd[14716]: NOQUEUE: reject: RCPT from unknown[103.28.106.55]: 450 4.7.25 Client host rejected: cannot find your hostname, [103.28.106.55]; from= to= proto=ESMTP helo=

          2. Hi mas,
            Coba konfigurasikan baris check_client_access lmdb:/opt/zimbra/conf/postfix_rbl_override diposisi paling atas

          3. Hi mas iman, terimaksih banyak atas respon nya , sudah saya coba posisikan di atas , baris check_client_access lmdb:/opt/zimbra/conf/postfix_rbl_override nya ,
            zimbra@mail:~$ zmprov gacf | grep zimbraMtaRestriction
            zimbraMtaRestriction: check_policy_service inet:127.0.0.1:10031
            zimbraMtaRestriction: check_client_access lmdb:/opt/zimbra/conf/postfix_rbl_override
            zimbraMtaRestriction: reject_invalid_helo_hostname
            zimbraMtaRestriction: reject_non_fqdn_sender
            zimbraMtaRestriction: reject_unknown_client_hostname
            zimbraMtaRestriction: reject_rbl_client b.barracudacentral.org
            zimbraMtaRestriction: reject_rbl_client zen.spamhaus.org
            zimbraMtaRestriction: reject_rbl_client psbl.surriel.com
            zimbraMtaRestriction: reject_rbl_client cbl.abuseat.org
            zimbraMtaRestriction: reject_rbl_client bl.spamcop.net
            zimbraMtaRestriction: reject_rhsbl_client dbl.spamhaus.org
            zimbraMtaRestriction: reject_rhsbl_client multi.surbl.org

            tapi masih di reject mas email yang coba saya white list

            Mar 17 09:13:58 mail postfix/smtpd[21290]: NOQUEUE: reject: RCPT from unknown[114.5.55.8]: 450 4.7.25 Client host rejected: cannot find your hostname, [114.5.55.8]; from= to= proto=ESMTP helo=

            mohon saran nya, terimaksih banyak sebelum nya 🙂

          4. Hi mas Aldy,

            Hhmm, agak aneh sih mas. Mungkin bisa info ke Admin email pengirim agar dibuatkan PTR nya. Cara tersebut lebih aman dan rekomendasi menurut saya

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