No PTR record according to gmail

Question

Recently, I installed iredmail on my VPS and configured DNS records (including ptr). It confirms nslookup:

 nslookup zelenin.top
Name:   zelenin.top
Address: 191.101.251.182
 nslookup -query=mx zelenin.top
zelenin.top mail exchanger = 5 mail.zelenin.top.
 nslookup 191.101.251.182
182.251.101.191.in-addr.arpa    name = mail.zelenin.top.

I also configure DKIM, SPF, DMARC and google-site-verification records. Then I connected to the VPS by mail client and tried to send mail to gmail. But it was not delivered, and I got an answer:

host gmail-smtp-in.l.google.com[2a00:1450:4013:c01::1a] said: 550-5.7.1
[2a00:7c80:0:58::1:600] The IP address sending this message does not
550-5.7.1 have a PTR record setup. As a policy, Gmail does not accept
messages 550-5.7.1 from IPs with missing PTR records. Please visit
550-5.7.1  https://support.google.com/mail/answer/81126#authentication for
more 550 5.7.1 information. m65si25883044wmd.98 - gsmtp (in reply to end of
DATA command)

I don not know what information may be helpful or what can cause this. Thank you.

Solution

There doesn't appear to exist any PTR record for the IP address your mail was sent from (according to the error message: 2a00:7c80:0:58::1:600).

$ dig -x 2a00:7c80:0:58::1:600

; <<>> DiG 9.10.3-P3-RedHat-9.10.3-10.P3.fc23 <<>> -x 2a00:7c80:0:58::1:600
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 31932
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;0.0.6.0.1.0.0.0.0.0.0.0.0.0.0.0.8.5.0.0.0.0.0.0.0.8.c.7.0.0.a.2.ip6.arpa. IN PTR

;; AUTHORITY SECTION:
0.8.c.7.0.0.a.2.ip6.arpa. 3600  IN      SOA     ns1.worldstream.nl. hostmaster.worldstream.nl. 2016022000 10800 3600 604800 3600

;; Query time: 166 msec
;; SERVER: 139.162.131.5#53(139.162.131.5)
;; WHEN: Sun Feb 21 11:58:22 UTC 2016
;; MSG SIZE  rcvd: 166

$

(Particularly note the NXDOMAIN status and the only included data being a SOA record in authority section.)

Could it be that you have set up PTR records only for your IPv4 addresses and not IPv6?

Comments

[Jacob Evans]

If you don't know how to bind and rdns your ipv6 address, you should disable ipv6 on SMTP

[Vladislav]

Thanks for fast answer. I do have several ipv6 addreses on my VPS, but i do not use them at all. There is no AAAA record, and the only mx record is pointing to my A ipv4 record. Is it possible, that postfix uses wrong ip for transferring email? And if so, can you please tell me, where should I change my config to avoid it?

[Håkan Lindqvist]

@Vladislav Which address is the right address? MX records for your own domain have nothing to do with which address you use to send mail. If you have a dual-stack mail server I presume you would want to pick one IPv4 and one IPv6 address.

[Vladislav]

Honestly, I am not sure, which type is my server, but I definitely can use an IPv6 address. So I just need to add an AAAA record and create PTR record for it? Thing is, i have 8 IPv6 addresses, so I need to add them all? Or does postfix uses just one?

[Håkan Lindqvist]

@Vladislav It will use whichever address the host OS prefers for the destination (probably not changing unless you change the host configuration). You could force postfix to use specific addresses: serverfault.com/questions/92181/…