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Reverse PTR record on a shared box

Posted on 2007-04-04
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Last Modified: 2010-04-10
Hello,
  I have a dedicated hosting box with a hosting company.  People were complaining that they would try to send me an email and it would say user mailbox does not exist.  My hosting company said they need to create a reverse PTR record for me.  This seems to have fixed the problem for me but what about for my clients.  If someone tries to send an email to someone@AnotherDomainOnMyHost.com won't they need their own reverse PTR record since when they do a reverse dns lookup it will say mail.MyDomain.com?
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Question by:rickBergami
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by:Chris Dent
ID: 18853682

Not exactly.

The Reverse Lookup Record is there as a quick check to point out unofficial mail servers.

When your server sends out mail it should do so as mail.yourdomain.com. That won't change when you're sending mail for a different domain it's part of the SMTP servers configuration.

All the PTR record has to do is match that single mail.yourdomain.com entry.

Hope that makes sense.

Chris
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by:rickBergami
ID: 18853804
Thanks very much for your help.  So you are saying when one of my clients sends from mail.TheirDomain.com it just needs to be authenticated against mail.MyDomain.com (or mail.AnyDomain.com for that matter)?
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by:Chris Dent
ID: 18854019

If your server is sending their mail then it doesn't really matter much what domain they're sending from. Your server will send out as it's name, never anything else.

That still applies even if they access your mail server as mail.TheirDomain.com. It's not what they see, but what your server believes itself to be.

I hope that makes sense! :)

Chris
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by:rickBergami
ID: 18854139
Thanks Chis.  This has been very insightful.  The reason this started is because I had a friend of my contact me that some people were unable to email them and got a message saying this user did not exist.  I thought it might be because they do not have a reverse PTR record on their server.  Their host is godaddy.  I would think that a big company like godaddy would have this set up?  I contacted them and they said they do not support this feature but wouldn't they have something set up like mail.godaddy.com?
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Chris Dent earned 500 total points
ID: 18854275

For e-mail sent to a user it's unlikely that reverse DNS is responsible. That's where the Recipients server (yours in this case) checks that the Sending server is telling the truth about it's name - it's not something that happens by default, you'd have to configure it.

For the User does not exist type messages you must try and reproduce the problem when sending mail into your server. Generally we'd do this using Telnet. MS have a little article on how to do that:

http://support.microsoft.com/kb/153119

If you've tested that you can indeed receive messages for that user you should do a quick check of the MX Records for that domain. If you go to www.dnsreport.com and put the domain in it will show you a report on the MX Record configuration as well as a lot of other information.

Check that any entries in the MX Record are able to receive mail for the address concerned.

Chris
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