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Support Center » Knowledgebase » VisNetic MailServer » DNS - Understanding and getting it to working with VisNetic MailServer
 DNS - Understanding and getting it to working with VisNetic MailServer
Solution Having a domain, e.g. Deerfield.com, is an important step in establishing an identity for a business on the Internet. People enter the domain as part of an email address or a Web address. What the network uses to route traffic is not domain names as such, but the corresponding IP address. The translation between fully qualified domain names and IP addresses is taken care of by DNS servers. DNS server is an abbreviation for Domain Name System server. In brief, all the host names on the Internet are converted to IP addresses by querying the DNS. DNS has many purposes. The most important purpose is that without a proper DNS server your Internet connection cannot work because the real IP addresses of the desired servers are not able to be resolved.

DNS runs on a UDP protocol port 53.

There are several record types on DNS. For us the 2 important records are A and MX records. A-records convert host names into IP addresses.

MX records are mail exchange records. They are used for delivery of email to its destination mail server. Basically, an alias and a domain construct email addresses: alias@domain. Example: matt@deerfield.com. Each domain should have at least 1 MX record. If no MX record exists for a domain, there could potentially be problems delivering mail. There are some issues when it might work but generally all domains should have MX records.

Each MX record for a domain has a preference number and a host name of the server to deliver messages to. When there is more than 1 MX record for a domain, the lowest preference number has the highest priority and should be tried first to deliver the message to.

Example: deerfield.com MX mail.deerfield.com 10

The above is an MX record for the domain Deerfield.com with a preference 10.
Your ISP mainly maintains DNS servers. You should make sure they setup your DNS records correctly. If you need proper DNS records for your mail server you should do this:

Find out the IP of your mail server computer

  • Require an A DNS record such as mail.yourdomain.com to point to that IP
  • Require an MX DNS record for your domain to point to mail.yourdomain.com with some preference (10)
To enter DNS server IP addresses in VisNetic MailServer perform the following:

From the VisNetic MailServer Configuration console:

  1. Select System
  2. Enter the DNS server IP address(es) in the DNS field. Separate multiple DNS servers with a semi-colon (;)
  3. Click Save
  4. Click the Test DNS button to the right of the DNS field

With proper MX records your mail server can receive message from the Internet. In the VisNetic MailServer package there is a special tool that you can use to verify your DNS records. The tool is called �DNS query Tool� and can be found in:

C:\Program Files\Deerfield.com\VisNetic MailServer\dnsquery.exe

Run the tool. The DNS field should contain a proper working DNS server IP or host name. Query should contain the value you want to query. Type: select the DNS record type. Now verify all your DNS records. For deerfield.com it would be:

Query: deerfield.com, Type:MX, Result = mail.Deerfield.com

Query: mail.deerfield.com, Type: A, Result = {some IP address}

If your queries do not work either your specified DNS server is not working properly or your DNS records are not configured properly. You should call your ISP and ask them for their DNS server IP address and tell them to verify your records.

Additional DNS information is available at:

http://www.dnsstuff.com/

or

http://www.iptools.com


Article Details
Article ID: 83
Created On: Aug 13, 2004 11:19 AM

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