Understanding DNS to configure Merak Mail Server properly
This article explains the basics of how DNS (Domain Name System) works and how to check it is properly configured so you can send and receive mails to and from the Internet using your Merak Mail Server.
Introduction
The main method of communication between computers on the internet is via the TCP/IP protocol. Every machine connected to the Internet is assigned a unique identification - the IP (Internet Pointer) address, which is used to "address" data to the correct destination. For the Human user, however, trying to remember the IP address of every location on the Internet that you might want to visit would be a little difficult, so DNS was introduced to be a cross-reference between human-friendly names (like www.yahoo.com), and its corresponding IP address (216.109.118.64, for Yahoo).
DNS
DNS function via a network of DNS Servers spread around the internet, and they are queried whenever a host or domain name is used instead of an IP address. Without DNS servers the Internet just would not work.
EMail Servers communicate with each other to distribute mail, but they initially locate each other via DNS. If you Server does not have a valid DNS record then other servers will not be able to find you to deliver mail.
If you have Problems Receiving email
There are several record types on DNS. The two we are interested in are the "A" and "MX" types.
The A Record
The A (Address) records convert a host names into IP addresses.
Example:
www.yahoo.com A 216.109.118.64
The MX Record
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 no MX record for a domain - mail delivery will generally not work (there are some unusual cases when it will work but all domains should have MX records.). There is usually only 1 MX record for a domain., but there can be more.
Example:
icewarp.com MX mail.icewarp.com 10
The above is an MX record for the domain icewarp.com, which points at mail.icewarp.com as the mail server, with a preference setting of 10. The preference setting is useful when you have more than 1 MX record. It prioritises the order in which incoming servers should attempt to contact your servers. Lower preference is a higher priority.
How to check that your DNS is configured correctly for RECEIVING from the Internet?
IceWarp.com provides a tool with Merak Email Server to help you check your DNS records. It is call DNS Query Tool and can be started via
Start->Programs->Merak Mail Server->DNS Query Tools
Lets assume that your domain name is ICEWARP.COM and your Domain and Accounts are all set up correctly
Lets also assume that your Email Server Services are all running correctly (SMTP, POP3, IMAP).
Check the DNS Server setting in System->Internet Connection. It should contain a list of two or three DNS Server IP addresses, separated by semi-colons. If there are no DNS Servers listed you can choose some from here: http://80.247.230.136/dns.htm
Please note, that 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 .
Check your Mailserver Hostname in Mail Service->SMTP Service->General tab. It can be set to anything but it should match your DNS MX record
Now we can check the DNS server is configured correctly. We will check three items:
- The DNS server is working
- The MX Record for your domain is correct
- The IP address given by the MX Record can be contacted from the Internet
Is the DNS server working?
- Start the DNS Query Tool.
- Enter one of the DNS server names, or IP address, specified in your Merak Settings.
- Press the Lookup button.
- You should get a response in the main window, and an "OK" in the message bar at the bottom of the screen. This shows you have reached the DNS server correctly
- Repeat for all DNS Servers listed in your Merak Configuration
Is the MX Record for your domain correct?
- Enter you domain name in the Query: box (e.g. ICEWARP.COM).
- Select type Mail Exchange (MX).
- Press the Lookup button
You should get a result screen similar to the following:
The result column above indicates that the MX record for ICEWARP.COM points to server.icewarp.com. Your MX record should point to your hostname.
Is the server indicated by the MX Record reachable from the Internet
- Put in as a query the symbolic name from previous test (server.icewarp.com).
- Select Type Host Address (A).
- The result screen will show the IP address where your Merak Email Server is supposedly to be found. So we can try to access it.
To attempt access we will try to get into the Remote Configuration console of Merak. Your Merak Mail Controll/HTTP service must be running for this test to work
Open your browser and type in:
http://IPaddress:32000
e.g. http://83.208.16.57:32000 (from the above example).
If all is well you will be presented with the web login screen for Merak Email Server. If this doesn't happen you may need to speak to your technical support or system administrator for further assistance.
What to do, it you have problems SENDING emails to the Internet
Problems with outgoing messages not being are 99% of the time a DNS Server problem. Try specifying a different DNS server in System->Internet Connection and this will usually fix the problem.
If you still have problems sending emails then you should switch on SMTP logging (under System->Logging), try to send emails again and then analyse the logs
The logs are stored according to the settings in Storage->Directories tab:
Open the log path directory in Windows Explorer or any other kind file commander and sort the files by date. Open the last entry file.
Look for any failure messages in the log and they should give you an indication of the cause of the problem. You may need to investigate further with your System Administrator.