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450 Client host rejected: cannot find your hostname, [XX.XX.XX.XXX]

We recently switched over from using a POP3 service on our remote dedicated server to hosting email locally on an Exchange Server 2007 system. Most everything is going well except that some of our emails that we send out get bounce messages with the error "450 Client host rejected: cannot find your hostname, [XX.XX.XX.XXX]". The IP address that XX.XX.XX.XXX represents is the IP of our dedicated server which is what we use as the smart host in the form of mail.domain.com. Does anyone know how to correct this? Thanks

Michael Worsham

It seems to be a Reverse DNS problem you are experiencing. Check this solution for details:

https://www.experts-exchange.com/questions/21153839/Reverse-DNS-Question.html

ASKER

I read that post and it seemed to suggest that the ISP needed to fix the issue in DNS. However, I have direct access to the DNS server that hosts our site and would like to do this myself. The interface that I use is WHM (Web Host Manager). Can someone tell me how to correct this from there?

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Michael Worsham

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ASKER

I see. I will submit a ticket to the hosting company to do this. Our server name is elite.domain.com. Should the PTR be to domain.com or elite.domain.com?

ASKER

I just looked and noticed what M has written. WHM appears to have a PTR option in their DNS editor. Does that mean I can add it myself?

Michael Worsham

You can try it and see what happens. If it doesn't work, delete it and just let the ISP handle it.

ASKER

I added it and nothing happened. Same goes with the SPF record I tried to add. Maybe it needs to propagate.

There will be propagation time, but with reverse DNS it isn't usually that long. I would ask the hosting company whether that function works - it is not unusual for a feature to be in control panels and it doesn't work or doesn't update public DNS information.

Simon.

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ASKER

That would make sense. I tried using a tool at dnsstuff.com which showed that my changes were ineffective. When I put in a support ticket to get it added, they said it would take up to 24 hours to reflect on my end. Sometimes those guys aren't as knowledgable as they appear to be and I have to prod them to get things going. I will let you know if it works.

By the way, is an SPF record also rDNS?

SPF has nothing to do with reverse DNS or PTR records. It is an additional entry that you can put in to your DNS records which tells anyone else who queries for DNS records what servers can send email for your domain. However the use is so low that it cannot be used for a hard failure - scoring at best.

Simon.

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ASKER

It turns out that even though WHM has a PTR option for the DNS Editor, it doesn't actually function. I had the hosting company setup a PTR and an SPF record and now dnsstuff.com is showing that they have propagated. I tried to send a message to one of the people that has been blocking our email and it actually went through. Thanks for your help.