IPv6 only host will be rejected by resolve-helo-identif

[maveric4911]

Hi,

we have discovered an issue with a german web hosting service provider, strato.
They have IPv6 only hostnames, what should not be a problem at all, but magicspam will reject this mail with:

Code: Select all

HELO argument [mo6-p00-ob.smtp.rzone.de] is missing a DNS entry

full log

Code: Select all

info@example.org
   Letzter Fehler: 550 5.7.0 
   Erklärung: host mail.example.de [2a01:ff:fff:fff::2] said: HELO argument 
              [mo6-p00-ob.smtp.rzone.de] is missing a DNS entry. See 
              http://spamauditor.org/best-practices/resolve-helo-identif
              ier/ for more information. Protection provided by 
              MagicSpam 2.0.5-1 http://www.magicspam.com

   Auszug aus dem Session-Protokoll:
   ... während der Kommunikation mit dem Mailserver mail.example.de [2a01:ff:fff:fff::2]:
   >>> RCPT TO:<info@example.org>
   <<< 550 5.7.0 HELO argument [mo6-p00-ob.smtp.rzone.de] is missing a DNS 
       entry. See 
       http://spamauditor.org/best-practices/resolve-helo-identifier/ 
       for more information. Protection provided by MagicSpam 2.0.5-1 
       http://www.magicspam.com

checking the DNS entries tells us, they have no A entry:

Code: Select all

 dig A mo6-p00-ob.smtp.rzone.de

; <<>> DiG 9.8.3-P1 <<>> A mo6-p00-ob.smtp.rzone.de
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39163
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;mo6-p00-ob.smtp.rzone.de.	IN	A

;; AUTHORITY SECTION:
rzone.de.		3600	IN	SOA	karlsruhe.nic.xlink.net. de-domain.xlink.net. 2016072800 86400 7200 604800 86400

;; Query time: 34 msec
;; SERVER: 172.17.3.1#53(172.17.3.1)
;; WHEN: Thu Jul 28 09:04:43 2016
;; MSG SIZE  rcvd: 111

but an AAAA entry:

Code: Select all

dig AAAA mo6-p00-ob.smtp.rzone.de
;; Truncated, retrying in TCP mode.

; <<>> DiG 9.8.3-P1 <<>> AAAA mo6-p00-ob.smtp.rzone.de
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26698
;; flags: qr rd ra; QUERY: 1, ANSWER: 12, AUTHORITY: 13, ADDITIONAL: 0

;; QUESTION SECTION:
;mo6-p00-ob.smtp.rzone.de.	IN	AAAA

;; ANSWER SECTION:
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::7
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::4
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::8
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::2
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::3
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::10
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::9
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::1
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::12
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::5
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::6
mo6-p00-ob.smtp.rzone.de. 86400	IN	AAAA	2a01:238:20a:202:5300::11

;; AUTHORITY SECTION:
.			28336	IN	NS	c.root-servers.net.
.			28336	IN	NS	b.root-servers.net.
.			28336	IN	NS	f.root-servers.net.
.			28336	IN	NS	l.root-servers.net.
.			28336	IN	NS	e.root-servers.net.
.			28336	IN	NS	a.root-servers.net.
.			28336	IN	NS	g.root-servers.net.
.			28336	IN	NS	d.root-servers.net.
.			28336	IN	NS	i.root-servers.net.
.			28336	IN	NS	k.root-servers.net.
.			28336	IN	NS	j.root-servers.net.
.			28336	IN	NS	m.root-servers.net.
.			28336	IN	NS	h.root-servers.net.

;; Query time: 93 msec
;; SERVER: 172.17.3.1#53(172.17.3.1)
;; WHEN: Thu Jul 28 09:04:56 2016
;; MSG SIZE  rcvd: 589

[magicspam]

Thank you for reporting this. We have passed this information over to our development team to review. It is still early days in development for SMTP service with IPv6, and we appreciate hearing about these type of issues to help work out all the issues with integrating in a full IPv6 world.

Thanks!