Reverse DNS to exchange or spam filter?
Hi, I have a company running exchange 2003 envoirment. One of our users I getting NRDs when sending to a particular domain. The error is #5.5.0 smtp;550 relay not permitted>. I can confirm that the issue is not with the recipient domain as I can send to this domain with no problem. My A records and MX records are setup correctly but I am thinking it is a reverse DNS issue which I know need to be set with the ISP but here is my questionMy incoming mail comes through cloud based spam filter so my setup is that my MX record points to say myspamfilter.com and the spam filter forwards the mail to my on premise exchange. Outgoing mail does not use smart host. This all works fine and I know the issue is nothing to spam filter cause outgoing mail does not touch spam filter but thats just a bit of background. I ran myspamfilter.com on MX lookup and the reverse DNS resolves ok but there is a SMTP banner warning Reverse DNS does not match SMTP Banner. Do I need to set reverse DNS with my ISP to point to myspamfilter.com or directly to my exchange server. Any help would be much appricared. Thanks.
June 21st, 2012 2:38pm

Hi, I have a company running exchange 2003 envoirment. One of our users I getting NRDs when sending to a particular domain. The error is #5.5.0 smtp;550 relay not permitted>. I can confirm that the issue is not with the recipient domain as I can send to this domain with no problem. My A records and MX records are setup correctly but I am thinking it is a reverse DNS issue which I know need to be set with the ISP but here is my questionMy incoming mail comes through cloud based spam filter so my setup is that my MX record points to say myspamfilter.com and the spam filter forwards the mail to my on premise exchange. This all works fine and I know the issue is nothing to spam filter cause outgoing mail does not touch spam filter but thats just a bit of background. I ran myspamfilter.com on MX lookup and the reverse DNS resolves ok but there is a SMTP banner warning Reverse DNS does not match SMTP Banner. Do I need to set reverse DNS with my ISP to point to myspamfilter.com or directly to my exchange server. Any help would be much appricared. Thanks.
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June 21st, 2012 3:01pm

On Thu, 21 Jun 2012 18:41:20 +0000, RainyDays84 wrote: > >I have a company running exchange 2003 envoirment. One of our users I getting NRDs when sending to a particular domain. The error is #5.5.0 smtp;550 relay not permitted>. I can confirm that the issue is not with the recipient domain as I can send to this domain with no problem. Check youe SMTP protocol log and verify that your server tried to deliver the message to the right IP address. It wouldn't be the first time that somone's left a secondary (or tertiary) MX record lying around in DNS that refers to a machine that no longer accepts mail for the domain. If the message was directed to the correct IP address then contact the admin and ask why their machine(s) rejected the RCPT TO. >My A records and MX records are setup correctly but I am thinking it is a reverse DNS issue which I know need to be set with the ISP but here is my questionMy incoming mail comes through cloud based spam filter so my setup is that my MX record points to say myspamfilter.com and the spam filter forwards the mail to my on premise exchange. This all works fine and I know the issue is nothing to spam filter cause outgoing mail does not touch spam filter but thats just a bit of background. I ran myspamfilter.com on MX lookup and the reverse DNS resolves ok but there is a SMTP banner warning Reverse DNS does not match SMTP Banner. Do I need to set reverse DNS with my ISP to point to myspamfilter.com or directly >to my exchange server. Any help would be much appricared. Your server's external IP address needs a PTR record. It really doesn't have to return the name that your server sends in the HELO\EHLO command, but it's not a bad idea if it does. --- Rich Matheisen MCSE+I, Exchange MVP --- Rich Matheisen MCSE+I, Exchange MVP
June 21st, 2012 10:44pm

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