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PTR - DNS - RDNS - SPAM

Posted on 2010-08-23
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Last Modified: 2013-12-09
Hi all:

This one is stumping me. A client started to get their e-mail flagged as SPAM by some mail hosts, one being a major cable company in the area. Now we have the website/DNS holder, my client and the cable company going back and forth about why it is happening and who is responsible.
We have a 2003 exchange server behind a basic firewall. All incoming mail is filtered through Postini and all outbound goes through Postini. All inbound is fine, some outbound is not. They have had this setup for 2 years without issue, and then it suddenly started happening a couple months ago. The website/DNS folks say we need to program a PTR record in our firewall (huh?) How do you program that, isn't that a DNS thing? Then they were on to SPF records. So I had Postini give me their SPF record info. It was added to DNS but to no avail.
Is the cable company looking at Postini's info or are they looking back to the originating server. Do I need an SPF for our server as well as Postini's?

Does that make sense? We are not on any blacklists that I have tested (mxtoolbox among them) .

Thoughts? Thanks!
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Question by:mattk-tcw
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BobintheNoc earned 250 total points
ID: 33508159
If you want to create a PTR record, you have to find out who is authoritative for the IP address.  This is usually your ISP.   The PTR record would be the reverse lookup of you IP address--producing, ideally, some form of a response like myhost.myisp.net.

Simply having ANY ptr record, not necessarily one that matches your mailhost's name is all that's usually needed.  To find out if your IP adress has a valid ptr, at a cmd prompt, you can use nslookup or any of the many DNS test sites on the web.  Enter your IP, see what comes back.  If no record is returned, you may have trouble delivering to some email domains that check for the presence of the PTR.

As for the SPF record--that's created within the DNS authority for your domain name.  Sometimes, this is your own server within your organization.  If you don't know this one already, then I'd bet your DNS is hosted somewhere else, perhaps at your domain's registrar.  Again, using nslookup or a DNS test web site, you can find the NS (name server) records for your domain name.  Contact whomever maintains/manages those name servers, and have them create your SPF record.  It's a simple text file, but there are a few options to consider.  There are several SPF assistance webs online--they'll even compose your SPF for you online, for free.  Your DNS provider may also help create one for you--chances are they'll know exactly what to do.

You will want to check the popular rbl/SBL (spam blocking lists) that your ip address may have shown up on.  If you find yourself on one, you can email the sbl maintainer and usually have your address removed--providing that you have remedied the source of the spam.

If it's coming from within your organization, you should consider blocking ALL outbound SMTP mail, except for your mail server.  Your mail server can also be configured to use a SMARTHOST to point to Postini--so that all outbound mail is sent through Postini instead of your mail server attempting to connect to each destination domain.

Spam and fighting spam is not a super easy thing to learn overnight.  These concepts should get you going in the right direction, I hope.  Just ask and we can elaborate.
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by:shauncroucher
shauncroucher earned 250 total points
ID: 33520967
"all outbound goes through Postini.."

So, you shouldn't have to do anything at all, as long as Postini accept mail from your server, talk to them and get them to resolve the issue.

Shaun
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Author Comment

by:mattk-tcw
ID: 33554715
After weeks over finger pointing between the cable compeny who was blocking up, our Web/DNS provider, my client and me ....... it turns out is was the cable compeny who put a block on our mail because "a few" of their suscribers had marked my client's marketing e-mails as SPAM rather than using the unsubscribe option on the e-mail itself. Of course we find this out after posting my questions here. Thanks for your help!
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by:mattk-tcw
ID: 33593995
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