Seth Charles via mailop wrote:
Hello,
We're running into a strange issue I'm wondering if anyone on this
list has seen before.
We have a client that is running into blocks at Gmail, and the reason
given is, "550 5.7.1 [167.89.88.20] The IP address sending this
message does not have a PTR record setup. As a policy, Gmail does not
accept messages from IPs with missing PTR records. Please visit
https://support.google.com/mail/answer/81126#authentication for more
information."
That's all fine, but we have verified through terminal digs as well as
tools like the Reverse Lookup at MXToolbox that there is a PTR record
in place and does point back to the proper value.
Terminal: (host 167.89.88.20
20.88.89.167.in-addr.arpa domain name pointer
o1.webmaillist.flowerdeliveryexpress.com
<http://o1.webmaillist.flowerdeliveryexpress.com>.)
MXToolbox:
Type IP Address Domain Name TTL
PTR 167.89.88.20
<http://mxtoolbox.com/SuperTool.aspx?action=a%3ao1.webmaillist.flowerdeliveryexpress.com.&run=networktools#>
o1.webmaillist.flowerdeliveryexpress.com
<http://mxtoolbox.com/SuperTool.aspx?action=a%3ao1.webmaillist.flowerdeliveryexpress.com.&run=networktools#>
15 min
The two affected IPs are:
167.89.88.20
167.89.89.136
Anyone running into similar issues or have any insights?
I believe (see below) that a PTR is only considered valid if there is a
matching A record... and on a personal note, I wouldn't be trusting a
PTR with a 15minute TTL, that just reeks of "I'm going to change it at
the first sign of trouble"
From RFC1912 Sec 2.1:
Also,
PTR records must point back to a valid A record, not a alias defined
by a CNAME.
Also note the wording "must" unlike the following text preceding that
above that just says, "should":
Make sure your PTR and A records match. For every IP address, there
should be a matching PTR record in the in-addr.arpa domain.
This to me reads:
You should have a PTR record for every A record though it is not required.
If you have a PTR record there has to be a matching A record, it is
required.
Regards,
Michelle
--
Michelle Sullivan
http://www.mhix.org/
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