Configure Change E-Mail Server Reverse DNS and MX Information Appropriately


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

On this article I’ll describe easy methods to appropriately 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 observe the identical precept.

Assigning an IP handle

Ranging from the underside up the very first thing it’s worthwhile to do is assign a static exterior IP handle to the inner non-public handle of your mail server. You will have to use these guidelines in your firewall to port ahead SMTP (port 25) and NAT an exterior IP handle to the inner handle of the server.

One thing that a number of directors neglect to do or verify is to set the outgoing NAT rule to make use of the identical exterior IP handle created for the inbound rule to the mail server. If this is not set, Reverse DNS is not going to match and in flip your mail server can be listed on blacklists. In case your firewall guidelines are setup appropriately the IP handle listed on this web page ought to be the identical IP handle you mapped to the inner non-public IP handle of the mail server.

Create the MX information in your mail server

For the aim of this instance, listed under are all the main points of my mail server that will help you perceive what it’s worthwhile to do.

Exterior IP:

E-Mail Area:

You will have to be an administrative contact in your Exterior DNS supplier in your area to make these adjustments. Generally this may be accomplished via a web-based management panel via your DNS supplier. Failing that on the cellphone 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 handle mapped in your firewall to the mail server. The host A file could be referred to as any factor however is often referred to as “mail”. In our instance we’ll create “” to level to IP handle “”

2. Subsequent we’ll 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 handle is the basis area title in our case “”

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

The bottom property is essentially the most most well-liked however in our instance we’ll set the precedence as 10.

Use NSlookup to verify 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 verify our DNS entries are utilized and proper we will use nslookup.

1. Open a CMD immediate and kind nslookup

2. Sort set kind=mx

three. Sort the area title which in our case is

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


Non-authoritative reply: MX choice = 10, mail exchanger = web handle =

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 be sure that the IP handle of the mail A or host file in DNS is similar because the IP handle it’s speaking with. Just one RDNS entry could be current per IP handle.

To do that you will have to contact your ISP to make this entry. You will be unable to do that in your DNS management panel until 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 wish to create an RDNS entry for our IP handle 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 appropriate do the next:

1. Open a CMD immediate.

2. Sort Ping -a (That is the exterior IP handle in your mail server. In our case we use our exterior IP handle acknowledged above)

If RDNS is configured appropriately the next output can be proven:

C:UsersUser>ping -a

Pinging [] with 32 bytes of information:

SMTP Banner

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

Configure SMTP banner Change 2003

1. Open Change system supervisor.

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

three. Develop Servers.

four. Develop YourServerName.

5. Develop Protocals container.

6. Choose SMTP container.

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

choose Properties.

eight. Choose the Supply Tab.

9. Click on the Superior button.

10. Below the Totally-qualified area title kind (The A/Host file you created in DNS in your mail server)

11. Click on OK and OK once more to just accept the adjustments

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 proper choose the Ship Connectors tab.

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

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

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

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

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

To confirm these adjustments we will 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. Sort 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

010 17:51:20 +0000

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

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

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

Following these information traces will efficiently and appropriately configure mail routing to and out of your mail server. The subsequent step is just too safe and guarantee your mail server isn’t an open relay. I can be writing a separate article devoted to this within the close to future.

Supply by Mike S Collins


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