Configure Change E-Mail Server Reverse DNS and MX Data Accurately

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 implies that all of your inbound mail will likely be blocked for those who do occur to be listed on a spam blacklist.

On this article I’ll describe the right way to appropriately configure your MX and reverse DNS information on 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 you could do is assign a static exterior IP handle to the interior non-public handle of your mail server. You have to to use these guidelines in your firewall to port ahead SMTP (port 25) and NAT an exterior IP handle to the interior handle of the server.

One thing that loads of directors overlook to do or examine 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 will likely be listed on blacklists. In case your firewall guidelines are setup appropriately the IP handle listed on this web page needs to be the identical IP handle you mapped to the interior non-public IP handle of the mail server.

Create the MX information on your mail server

For the aim of this instance, listed under are all the main points of my mail server that can assist you perceive what you could do.

Exterior IP:

E-Mail Area:

You have to to be an administrative contact on your Exterior DNS supplier on your area to make these modifications. Usually this may be accomplished via an internet management panel via your DNS supplier. Failing that on the cellphone or through 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 will 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”. Ensure that the host handle is the foundation area identify 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 popular however in our instance we’ll set the precedence as 10.

Use NSlookup to examine DNS and MX information are utilized

It will possibly take as much as 48 hours for DNS to propagate however most often 12-24 hours. To examine our DNS entries are utilized and proper we will 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 appropriately setup:


Non-authoritative reply: MX desire = 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 ensure that the IP handle of the mail A or host file in DNS is identical because the IP handle it’s speaking with. Only one RDNS entry will be current per IP handle.

To do that you’ll need 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’d 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 take as much as 48 hours for DNS to propagate however most often 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 handle on your mail server. In our case we use our exterior IP handle acknowledged above)

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

C:UsersUser>ping -a

Pinging [] with 32 bytes of knowledge:

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 greatest apply is to have it as your mail host/A file.

Configure SMTP banner Change 2003

1. Open Change system supervisor.

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

three. Broaden Servers.

four. Broaden YourServerName.

5. Broaden Protocals container.

6. Choose SMTP container.

7. On the proper 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. Underneath the Absolutely-qualified area identify kind (The A/Host file you created in DNS on 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 proper choose the Ship Connectors tab.

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

6. On the Common 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. Underneath 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 Common 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 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. Kind Telnet 25.

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

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

010 17:51:20 +0000

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

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

An important 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 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 simply too safe and guarantee your mail server is just not an open relay. I will likely be writing a separate article devoted to this within the close to future.

Source by Mike S Collins

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