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Reverse DNS Problem - 19.Jul.2007 3:41:17 AM

trevorc

Posts: 64
Joined: 11.Jul.2006
Status: offline

Hi, i have 2 Exchange 2K SP3 each running on Win 2K Server SP4. One of these (MAIL1) is a DC, GC, DNS, WINS whilst the other (MAIL2) is just a member server.

Mail is sent to MAIL2 and is then routed onto MAIL1 via AD.

I had asked my ISP to set Reverse DNS for our domain. I also set Reverse DNS on both Exchange servers so i should be working fine. I send a receive emails from everyone except this 1 particular domain: tominomalta.com. Whenever i send an email to this domain, i receive a NDR saying:

You do not have permission to send to this recipient. For assistance, contact your system administrator.
<mail.DOMAIN.com.mt #5.7.1 smtp;550 5.7.1 Fix reverse DNS for 1.2.3.4,or use your ISP server>

For the sake of security, in this message i renamed the original domain to DOMAIN and put 1.2.3.4 instead of the original IP address.

The strange thing is that 1.2.3.4 is not our MX record and that may be the reason why tominomalta is not resolving DOMAIN.com to it's original MX record. 1.2.3.4 is our modem's IP.

Do you think i should ask my ISP to set reverse DNS on our modem's IP too? Can it be done?

I will therefore end up with 1 MX Record with Reverse DNS and my modem's IP which when Reverse DNS is done points to our domain too.

I hope someone understands me

_____________________________

Trevor Camilleri
ATD, MCP

Post #: 1

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RE: Reverse DNS Problem - 19.Jul.2007 10:14:18 AM

uemurad

Posts: 5485
Joined: 7.Jan.2004
From: California, USA
Status: online

The addresses for which you need to configure reverse DNS (via a PTR record) are the ones from which you are sending out SMTP traffic. If more than one of your servers communicates with outside SMTP servers, each one of those public IP addresses should have a PTR record identifying itself as belonging to your public SMTP domain.

For some reason the external domain thinks your messages are coming from 1.2.3.4. The question to answer is, "Why would it think that?"

_____________________________

Regards,

Dean T. Uemura
Microsoft MVP - Exchange
exchangeguy.blogspot.com
uemurad@yahoo.com

(in reply to trevorc)

Post #: 2