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Reverse DNS Setup -- what name should I use in the reverse lookup record

WallaceR
WallaceR asked
on
Medium Priority
1,153 Views
Last Modified: 2010-05-18
I think this is a fairly quick and easy question...

I am sending email from user@publicdomain.com and my exchange server is ComputerName.PrivateDomain.com

Should my rDNS record reflect mail.publicdomain.com or ComputerName.PrivateDomain.com

I am doing this to fix sending email to AOL and Comcast.  (the returned message mentions my private computer name and domain)

Thanks so much for any help,

WallaceR
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You need to have a pointer record going to ComputerName.PrivateDomain.com (the exchange server).


check this out to too:

http://www.experts-exchange.com/Networking/Q_21764044.html
You dont fix this in your AD DNS server if that's what you are asking.

You have to get your ISP who owns the IP address you are on for sending email to setup the rdns.  A ip to name resolution should reslove the IP to whatever your mail server's external hostname is, example mail.domain.com

Author

Commented:
Let me clarify my question -- I am asking what I should tell my ISP the rDNS record should respond with -- whether it is mail.publicdomain.com or computername.internaldomain.com (or .local if I had set it up right).  The error I received from Comcast which is confusing me:

<(computer.localdomain.com) #5.5.0 smtp;521-EHLO/HELO from sender xxx.168.229.90 does not map to (computer.localdomain.com) in DNS>

where the "(computer.localdomain.com)" is from my local AD structure (the local machine name etc...) and not my mail.

Do I need to setup my local exchange server to show the public domain to the world or will it always show the local server name?
When NAT is being used

In cases where NAT (Network Address Translation) is being used you will need to provide you ISP with the IP address of your external NAT interface, and configure your NAT device with Static Mapping for TCP Port 25, and have all TCP Port 25 traffic forwarded to the internal IP address of your mail server.

Let's say you have the following LAN configuration:

                                        Internet
                                             |
                                             |
                                             |
                                             |
                                             |
                                   192.90.1.1/29 (Real IP from ISP)
                                             |
                                Internet Router + NAT
                                             |
                                   192.168.0.1 (Bogus IP)
                                             |
                                             |
                                             |
                                             |
                                             |
Mail Server----------------Switching Hub
192.168.0.10                          |  
(Bogus IP)                              |  
                                             |
                                             |
                                             |
                                             |
                                             |
                                             |
                              Rest of internal network

In the above example you need to give the NAT's IP address as your MX Record.

Domain name: publicdomain.com

Record FQDN
 Record Type
 Record Value
 MX Pref
 
mail.publicdomain.com
 A
 192.90.1.1
 
 
publicdomain.com
 MX
 mail.publicdomain.com
 10
 

Note: Make sure you properly configure the NAT device to forward all TCP Port 25 traffic to 192.168.0.10.

Keith AlabasterEnterprise Architect
CERTIFIED EXPERT
Top Expert 2008
Commented:
mail.publicdomain.com

Unless you have been delegated contol of the reverse dns covering your external assigned ip addresses, the ISP will do this for you. In addition, your email MUST then leave your external firewall using that IP address else you will have defeated the object....

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in SMTP virtual server to reply with mail.yourdomain.com (make it the same as your MX record says the name of your email server)

go to delivery tab -> advanced -> FQDN

restart SMTP
telnet <internal IP of server> 25
should respond with mail.domain.com at the end
comcastic
Keith AlabasterEnterprise Architect
CERTIFIED EXPERT
Top Expert 2008

Commented:
Thank you :)
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