Annotation

This article is explaining basics of how DNS works and how to check, if is properly configured, to be able to send and receive mails from/to the Internet using your Merak Mail Server.

Introduction

     1. What to do, if you have problems RECEIVEING mails from the Internet
     2. What to do, it you have problems SENDING mails to the Internet

Introduction

All computers on the Internet are talking together mostly by TCP/IP protocol. Each user connected to the Internet has assigned the unique identification - IP (Internet Pointer) address. But searching users based on IP addresses would be very hard (imagine remember for each WWW site a 12 digit number...) and so the IP addresses are getting assigned the symbolic names.

Type into your Browser: http://64.58.76.222/

and you will get to the YAHOO!

The IP address 216.32.74.55 is translated to the WWW site WWW.YAHOO.COM .

This IP to symbolic name translations are done by DNS servers.

DNS server is an abbreviation for Domain Name System server. Basically all host names on the Internet are converted to IP addresses by querying the DNS.

DNS has many purposes. The most important one is that without a properly setupped DNS server your Internet connection cannot work.

If you want to be able SEND and RECEIVE an email from your server – you must be correctly setupped at DNS server.

DNS servers are mainly maintained by your ISP. You should make sure they setup your DNS records correctly. If they are not, your mail server will not be able to work right!

If you installed Merak Mail Server at your office LAN – and it works – and you
are not able to receive mails from the Internet, it is almost always problem

with incorrectly configured DNS server or your firewall.

2. What to do, if you have problems RECEIVING mails from the Internet

There are several record types on DNS. The two most important are
A and MX records.

A (Address) records convert a host names into IP addresses.

Example:

www.icewarp.com A 12.107.133.12

MX records are mail exchange records.

They are used for delivery of email to its destination mail sever. Basically email addresses are constructed by an alias and a domain: alias@domain. Example: info@icewarp.com. Each domain should have at least 1 MX record.

If there is none MX record for domain - mail delivery will not work. (There are some issues when it might work but generally all domains should have MX records.) Usually there is only 1 MX record for a domain.

Example:

icewarp.com MX mail.icewarp.com 10

The above is an MX record for the domain icewarp.com with a preference 10.

How to check, that your DNS is configured correctly for RECEIVING from the Internet

You really do not need to be a computer GURU for that. There is a tool called DNS Query Tool, which is coming for free together with the Merak. To run this tool go to the:

Start/Programs/Merak Mail Server/DNS Query Tool

Lets assume, that your domain name is: ICEWARP.COM and you want to receive mail for users of this domain. This domain you already established in the Merak Mail server and your Account folder looks like that :

Then check the System Folder. If everything is O.K, all three services of the Merak Mail Server are running (see 3 green lights in the middle of the screen) and you have checked DNS Query Lookup. Notice, that DNS field contains values: ns1.dn.net;ns2.dn.net

You do not need to change these values to “your ISP” DNS names.
All DNS servers in the whole world are replicated. Your Merak Mail Server will
work with ANY DNS server .

The Mail Server Hostname can by also anything, it is just identification of your server when is “speaking” with the other servers – you can put even your company name there .

Finally your System screen should look like this one:

Now we can finally start testing, to see if our DNS server is configured correctly. We need to check only three “checkpoints”:

1. DNS server is working

2. Find if there is a MX Record for your domain and where points

3. Find if the IP address where the MX Record points can be reached from the Internet

1. DNS server is working

Run DNS Query Tool and type in the DNS server name or IP address you want to approve. The good idea is to test the same DNS server as is in your System configuration. If everything is O.K., you can read a message in the left corner of the DNS Query Tool:
DNS Server Response 0 – OK

2. Find if there is MX Record for your domain and where points

We are checking domain ICEWARP.COM. Put the domain name as a Query and select type Mail Exchange (MX). You should get a result screen:

You can read, that MX record for domain ICEWARP.COM points to the symbolic name: mail.icewarp.com. All we need to find is, whether IP address of the computer, where is installed Merak Mail Server is the same as a IP address for symbolic name mail.icewarp.com.

.

3. Find if the IP address where MX Record points can be reached from the Internet

Put in as a query the symbolic name from previous test (mail.icewarp.com) and select Type Host Address (A). The result screen have to point to some IP address. This is IP address, where is supposed your Merak Mail Server to be installed.

And last, final test, is to find that your Merak Mail Server is running at this IP address. The computer GURU’s will use probably TELNET, but there is more simple way too. Each Merak can be remotely configured via TCP/IP. If your Merak Mail Controll/HTTP service is running Open your browser and type in:

http://your IP address:32000 e.g. http://194.108.176.130:32000

(you can use also symbolic name instead of IP address)

It will bring you to the “WEB Log-On screen of the Merak Mail Server.

3. What to do, it you have problems SENDING mails to the Internet

Receiving messages should be fine by now.

Sometimes there might be problems with sending messages. They might get stuck in the Outgoing queue. - nn MERAK it is the Merak\Mail\Forward directory.

99% it is a DNS server problem.

Not a DNS record problem but your DNS specification in the MERAK configuration program the system section DNS field.

Try to specify another DNS server there (assuming you are using DNS Lookup option).

If it still does not work switch on MERAK SMTP logging and analyze the logs. This LOG can be accessed remotely – using WEB based access, or locally. It is located in the Option folder of the Merak configuration.

Notice, that the LOG at the SMTP is checked at our demo screen. DEFAULT IS UNCHEK, so check it first and send some messages if you want to analyze the content of your SMTP LOG file.

Click the Show button at SMTP.

Look for Client Session records and MX queries. It should look like this:

Client session MX - Issuing query 194.213.224.2 for "icewarp.com"

The line above tells there is going to be a query to the DNS server 194.213.224.2 for the domain icewarp.com

The most important record is the following line:

Client session MX - Query response: 0 (1)

That line means DNS server responded with 0 (OK) and returned 1 result. If you have a different line such as Could not connect. Your DNS server is not working and you should use a different one. If your line looks like this:

Client session MX - Query response: 0 (0)

It is the same problem as above. Use a different DNS server.

Final lines of interest:

Client session Connecting to "mail.icewarp.com"

Client session Connected

The result of the DNS query returned host mail.icewarp.com and MERAK is trying to connect to it. It was successful. Sometimes you might get Could not connect. That means the remote server is either down or your machine cannot connect to it for some reason (firewall or incorrectly set up Internet connection etc.).

Try using this from the command line:

telnet mail.icewarp.com 25

If that works all your Internet settings are correct and the remote mail server that did not work and is only down for a some while.