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KB12062201 A DNS Primer

In order for Mailtraq to be your mail server (and also to serve webmail and allow external users to access the server) for your organization you have to tell the Internet world 'who you are' and 'where you are'.

'Who you are' 
You will need a domain name - for example, ours is:

'Where you are' Tip
When you register your domain name, you also get several 'records' which tell Internet traffic how to locate your servers.

Your 'A-record' for 'www.' holds the IP address of your website.

Your 'MX-record' (MX stands for 'mail exchange') says where your mail server is located.

Before you start

1 - Static IP Address
In order to run your own mail server direct on the Internet you must have a permanent Internet connection with a Static (fixed) IP address. Business Internet connections normally have fixed IP addresses, and it is usually possible to ask your ISP for one for SO-HO or home use.  There may be a small charge for doing this. Your ISP must also

2 - Port 25 access
You must check that your ISP allows traffic on Port 25. Business Internet connections normally have Port 25 open, but if you are transitioning a 
SO-HO or home use account you must confirm this is open. Port 25 is the route messages take to the Internet so it is essential it is open. You can use Telnet to check this yourself, using Port 25.

Once you have the Mail-host set (see below) you can use that for accessing webmail, for example:

You can also use it in email client configuration dialogs, for example:

If your email is currently being handled by someone else - commonly your ISP - you will need to tell the domain name registrar (where you registered your domain) to change your MX record to point to the Mailtraq machine. You can often do this yourself.

For technical reasons, an MX-record has to point to a domain, and then that domain points to the IP-address.
So, typically you set the MX-record to point to to a sub-domain you create yourself, for example - and then set to point to the public IP-address of your router. We explain how to do this below.

Changes do not happen instantly. DNS record changes typically take 24-48 hours to promulgate.

You can check that your MX record is correct by using a public checking service such as or using NSLookup on your own machine.

Meanwhile, do not stop your current POP3 collection from your ISP (or other mail host) - so that no messages get missed. Once you are confident that all mail is being routed direct by SMTP then you can stop the POP3 collection - waiting a few days is good.

'How do I get from my Internet connection to Mailtraq?'

If you connect to the Internet via a router - and most people do - then you will need to configure port forwarding or NAT to route traffic for certain ports to the Mailtraq machine. You may also need to open any firewalls on these ports.

The ports in question are:

Port 25 - SMTP
Port 110 - POP3
Port 143 - IMAP
Port 80 - Webmail

Don't worry about network security on these port forwards - Mailtraq provides an internal firewall to protect your local network.


Setting your A-Records

You register your domain with a Domain Registrar. This may be your ISP, but is more often a company who specializes in domain registration - there are many to choose from (click to see). Nearly all Registrars allow you change your own settings using some sort of 'console'.

The setting changes you need to make are simple - you need to set the A-Record for your mail DNS-host to the Public Facing IP Address of your Internet connection. Your ISP will have told you that when you signed up, and it is probably on your billing statement, but you can use the tool in this box to check at any time. You must test from a browser on the actual machine you have installed Mailtraq onto.

What is my Public Facing IP Address?
Use this link from the Mailtraq machine itself. 


The MX-Record

Be careful - the basic A-Record is the www A-Record. That will point to your website server, and does not normally need to be changed. Often it will be set as a catch-all entry '@', so 'www' points to '@'

Actions required
First - you must create an additional host (A-Record) for your domain, say: must point to the Public Facing IP Address of the machine that Mailtraq is installed onto.

Second - the MX-Record must be set to point to the sub-domain you just created.

How to do this

Once you know your Public Facing IP address, go to your account at your Domain Registrar and select the 'Total DNS Control' or 'DNS Manager' option. It may be called something slightly different, but you need to see a dialog similar to the one below. Do not confuse this with 'Domain Forwarding' or 'Frame-set Redirect' which may be other options.


This is an example from GoDaddy - a popular Registrar.

Find the DNS Manager section and click the 'Launch' link. A new view will open - see below:


In this example we had found that our Mailtraq was installed onto a machine at


'Help! I don't have a Static IP Address'

If you have a dynamic IP address read this...


Create a 'mail' Host 
You need to use a  mail  A-record  as well as the host name 'www' .  In the above example the 'www' has been set to the catch-all '@' which 'Points-to' That is the IP address of the server hosting the website for the domain.

First, you may need to delete an existing 'mail' entry in the 'C-Names' (Aliases) section - and 'Save Host File'
Then, use the 'Quick Add' (or equivalent) button to add a 'mail' entry in the 'A' (Host) section - and 'Save Host File'.
This is necessary because MX should not point to C-Names.

In the above example:
A new mail Host A-Record has been created and set to 'Point-to'
That is the IP Address of the machine that Mailtraq is installed onto.


Set the MX Record


Go the the MX Section of the DNS Manager and change the settings so that the MX Points to the host you created previously.

In this example the MX-Record points to which in turn points to  which is the public facing IP address of the machine hosting Mailtraq.



Strictly speaking in many cases you don't need an A-Record to access Mailtraq from 'outside'. If you know the IP address you can use that instead.

You can collect and send messages by using the IP address of the Mailtraq machine's Internet connection when asked for 'My SMTP server is...', or 'My IMAP Server is...'

You cannot receive messages from the Internet however unless you set a relationship between your IP address and your domain using the MX record in the DNS system explained above.

Keywords: kb general
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