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Any domain name has a DNS zone that consists of the following records:

'''A Record''' specifies IP addresses corresponding to your domain and its subdomains; '''CNAME record'''  specifies redirects from your domain's subdomains to other domains / subdomains; '''MX record''' specifies the mail server the emails for your domain should be delivered to; '''NS record'''  specifies the domain nameservers; '''SOA Record'''  Start of Authority record. It is the first entry in the zone file; '''PTR Record''' - Reverse pointer record. '''SPF Record'''- Sender Policy Framework (SPF) is an attempt to control forged e-mail.

<center>'''A Record'''</center>

An A (address) record is a DNS record that can be used to point your domain name and host names to a static IP address.

<center>'''CNAME Record'''</center>

Short for canonical name, also referred to as a CNAME record, a record in a DNS database that indicates the true, or canonical, host name of a computer that its aliases are associated with. A computer that hosts a Web site must have an IP address in order to be connected to the World Wide Web. The DNS resolves the computer’s domain name to its IP address, but there are cases when more than one domain name resolves to the same IP address, and this is where the CNAME is useful. A machine can have an unlimited number of CNAME aliases, but each alias must have a separate CNAME record in the database.


<center>'''MX Record'''</center>

Short form for mail exchange record, an entry in a domain name database that identifies the mail server responsible for domain's  e-mails handling. "Mail exchange" is just another name for the machine used for receiving and sending email.

When a domain name has more than one MX record, then these records can be prioritized with a preference number that indicates the order in which the mail servers should be used. Mailers attempt to deliver to the mail exchanger with the lowest preference value (highest priority). If the highest priority mail exchanger fails, the mailer will attempt to deliver to the next highest priority.

<center>'''PTR Record'''</center>

It is used to convert IP-addresses to host names.

For example, the A record for myidealhost.com resolves this domain name to 178.63.79.205:

And then the PTR record resolves 178.63.79.205 back to myidealhost.com:


<center>'''NS Record'''</center>

Name server records allow you to identify the authoritative servers for this zone. Each domain must have NS records as without them, the servers for a domain would be unknown.

<center>'''SOA Record'''</center>

The first entry in each of the zone files is the Start of Authority (SOA) resource record. The SOA record indicates the authoritative name server for this domain. Since the SOA record marks the beginning of a zone, there can be only one for each zone.

The SOA record stores the following information: 

the name of the server supplying the data for the zone; 

the zone administrator; 

the current version of the data file; 

the number of seconds a secondary name server should wait before checking for updates; 

the number of seconds a secondary name server should wait before retrying a failed zone transfer, etc.

<center>'''SPF Record'''</center>

Sender Policy Framework (SPF) record allows the domain owners to specify the hosts which are permitted to send email on behalf of their domains. Normal SMTP allows any computer to send an email claiming to be from anyone. Thus, it's easy for spammers to send emails with forged From: addresses. SPF allows a domain owner to  specify which machines or hosts are authorized to transmit email for their domain.

For example, you can designate which hosts are authorized to send email originating from user@your-domain.com. Your recipient's servers will then check the SPF record to identify the origin of your message.


Having SPF record set up will ensure that messages sent from users in your domain are not rejected by the recipient's domain.
Return to DNS records.
Retrieved from "http://myidealhost.com/tutorials/DNS_records"
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