Configure Exchange E-Mail Server Reverse DNS and MX Records Correctly

If DNS is setup incorrectly, over time your mail server IP will likely be added to blacklists. These days most E-Mail servers have some form of spam safety service which in flip signifies that all of your inbound mail will likely be blocked when you do occur to be listed on a spam blacklist.

On this article I’ll describe how one can accurately configure your MX and reverse DNS information in your mail server. This text relies on an Change 2003/2007 server however each different messaging server will comply with the identical precept.

Assigning an IP tackle

Ranging from the underside up the very first thing it’s essential do is assign a static exterior IP tackle to the interior personal tackle of your mail server. You will want to use these guidelines in your firewall to port ahead SMTP (port 25) and NAT an exterior IP tackle to the interior tackle of the server.

One thing that numerous directors overlook to do or examine is to set the outgoing NAT rule to make use of the identical exterior IP tackle created for the inbound rule to the mail server. If this is not set, Reverse DNS won’t match and in flip your mail server will likely be listed on blacklists. In case your firewall guidelines are setup accurately the IP tackle listed on this web page needs to be the identical IP tackle you mapped to the interior personal IP tackle of the mail server.

Create the MX information in your mail server

For the aim of this instance, listed beneath are all the small print of my mail server that will help you perceive what it’s essential do.

Exterior IP:

E-Mail Area:

You will want to be an administrative contact in your Exterior DNS supplier in your area to make these modifications. Typically this may be carried out by an internet management panel by your DNS supplier. Failing that on the telephone or by way of E-Mail.

1. The very first thing we have to do is create an A file to level to the exterior IP tackle mapped in your firewall to the mail server. The host A file may be known as any factor however is usually known as “mail”. In our instance we are going to create “” to level to IP tackle “”

2. Subsequent we are going to create an MX file to level to the newly created A file of our mail server.

Inside your DNS management panel choose “add MX file”. Make it possible for the host tackle is the basis area identify in our case “”

Set the FQDN because the A file we simply created which in our case is “”.

The bottom property is probably the most most well-liked however in our instance we are going to set the precedence as 10.

Use NSlookup to examine DNS and MX information are utilized

It might probably take as much as 48 hours for DNS to propagate however normally 12-24 hours. To examine our DNS entries are utilized and proper we are able to use nslookup.

1. Open a CMD immediate and kind nslookup

2. Kind set kind=mx

three. Kind the area identify which in our case is

In our instance the output ought to learn as follows if accurately setup:


Non-authoritative reply: MX desire = 10, mail exchanger = web tackle =

Configure Reverse DNS

Reverse DNS is used to confirm that the mail server is who it says it’s. The recipients mail server will do a reverse lookup to guarantee that the IP tackle of the mail A or host file in DNS is similar because the IP tackle it’s speaking with. Just one RDNS entry may be current per IP tackle.

To do that you have to to contact your ISP to make this entry. You won’t be able to do that in your DNS management panel except your ISP additionally host your DNS and provide the performance so as to add your individual RDNS information.

In our case we might contact our ISP and advise that we want to create an RDNS entry for our IP tackle which might resolve too

Confirm Reverse DNS

Once more it may well take as much as 48 hours for DNS to propagate however normally 12-24 hours. To confirm that the RDNS entries have been added and are right do the next:

1. Open a CMD immediate.

2. Kind Ping -a (That is the exterior IP tackle in your mail server. In our case we use our exterior IP tackle said above)

If RDNS is configured accurately the next output will likely be proven:

C:UsersUser>ping -a

Pinging [] with 32 bytes of information:

SMTP Banner

Each time a mail server establishes a connection together with your mail server it reveals its SMTP banner. This banner have to be resolvable on the web and greatest follow is to have it as your mail host/A file.

Configure SMTP banner Change 2003

1. Open Change system supervisor.

2. Increase your administrative group (“First administrative group” by default).

three. Increase Servers.

four. Increase YourServerName.

5. Increase Protocals container.

6. Choose SMTP container.

7. On the best window, proper click on the Default SMTP digital Server (Or the identify you set your SMTP Server) and

choose Properties.

eight. Choose the Supply Tab.

9. Click on the Superior button.

10. Beneath the Absolutely-qualified area identify kind (The A/Host file you created in DNS in your mail server)

11. Click on OK and OK once more to simply accept the modifications

Configure SMTP banner Change 2007/2010

1. Open the Change administration console.

2. Choose the Organisation Configuration container.

three. Choose Hub Transport container.

four. On the best choose the Ship Connectors tab.

5. Proper click on your ship connector and choose properties.

6. On the Basic tab underneath the Set the FQDN this connector will… kind the A file area identify you created. Which in our case is Click on OK.

7. Beneath the Server Configuration container click on the Hub Transport container.

eight. Within the Proper window Choose the properties of the Obtain Connector underneath Obtain Connectors tab.

9. On the Basic tab underneath the Set the FQDN this connector will… kind the A file area identify you created. Which in our case is Click on OK

To confirm these modifications we are able to use telnet to view the output upon establishing a connection on port 25 to our mail server. Use the next steps to do that:

1. Open a CMD immediate

2. Kind Telnet 25.

The output you see ought to look one thing like this and comprise your A file of your mail server:

220 Microsoft ESMTP MAIL Service prepared at Solar, 28 Feb 2

zero10 17:51:20 +0000

In the event you use an edge server or a SPAM filter equipment like a Barracuda the SMTP banner should be set on this system/server.

Examine to see in case your mail server is on spam lists and/or an open relay

An ideal web site to make use of to examine your MX information, RDNS, examine in case your mail server is an open relay and examine to see if you’re listed on spam lists is This can be a nice web site and one to maintain in your favourites.

Following these information strains will efficiently and accurately configure mail routing to and out of your mail server. The subsequent step is simply too safe and guarantee your mail server will not be an open relay. I will likely be writing a separate article devoted to this within the close to future.

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