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<div class="moz-cite-prefix">On 3/3/2014 11:26 AM, Stephen Malone
wrote:<br>
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<div class="WordSection1">
<p class="MsoNormal">Hi Folks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For PTR records out there that are pointing
to domains other than those that you control, I’m looking to
understand common practice around their setup. Two questions:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l0 level1 lfo2"><!--[if !supportLists]--><span
style="mso-list:Ignore">1.<span style="font:7.0pt
"Times New Roman"">
</span></span><!--[endif]-->In general, can I trust PTR
records? Is ownership of the target domain validated at setup
time by ISPs, and if yes, how is this done?<o:p></o:p></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l0 level1 lfo2"><!--[if !supportLists]--><span
style="mso-list:Ignore">2.<span style="font:7.0pt
"Times New Roman"">
</span></span><!--[endif]-->If ownership of PTR targets is
not routinely validated, is there a risk that the target
domain could be blacklisted by anti-spam providers?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Stephen Malone<o:p></o:p></p>
<p class="MsoNormal">Microsoft<o:p></o:p></p>
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<br>
</blockquote>
I am a smaller provider of email services to small businesses in the
local area.<br>
<br>
I send email from a given ip address. It's up to me to make sure
that the reverse records point back to the same host name that the
mail server uses during SMTP session setup. And further that the A
record for the host name during SMTP session setup(specifically in
the HELO or EHLO commands) matches.<br>
<br>
All of this is not revelent to the From or To or Reply to addresses,
either in the envelope or inside the email itself. More than one
domain can use a given SMTP server, but it's host name doesn't
change because of the From or Reply to fields in the HELO or EHLO
command lines.<br>
<br>
The PTR records 'belong' to the ISP that registers the addresses
from ARIN, RIPE, etc. The ISP can delegate the PTR records when a
block is assigned to a certain customer, but don't have to. It's up
to that ISP's policies to police those records.<br>
<br>
On the other hand, I don't care what the PTR shows for an ip address
I used two years ago. I only care for the PTR records for the ip
address I am using NOW. You won't have any knowledge of the ip
address used two years ago and won't be looking over there.<br>
<br>
Now I am not going to talk about SPF or DKIM or DomainKeys as I
don't use them extensively.<br>
<br>
Most blacklisting is done via ip address of the sending mail
server. Checks against domain names is an entirely different
subject and IMHO, not in the same league as this message.<br>
<br>
Lyle<br>
<br>
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