DomainKeys Identified Mail (DKIM) adds public key cryptography to the Simple Mail Transfer Protocol (SMTP). Email for the domain is digitally signed by the sending mail server using the private key for the domain. Receiving mail servers use the public key from the domain’s DKIM record to validate that messages have not been tampered with. …
Sender Policy Framework (SPF) records in the DNS identify the mail servers allowed to send email for a domain. SPF protects domains and their brands from email abuse by spammers and hackers. The Simple Mail Transfer Protocol (SMTP) is used to send email. SMTP does not include validation that the sending mail server is allowed …
The PTR or “pointer” DNS record type maps an IP address to a domain name in the DNS. This is called a DNS reverse lookup. Most DNS records types are used in “forward lookups”. A DNS forward lookup maps a DNS name to an IP address or another piece of DNS data. PTR records do …
The SRV or “service locator” DNS record type enables service discovery in the DNS. SRV records allow services to be advertised on specific ports and used in an order controlled by the owner of the service. SRV also provides a load balancing feature. The SRV record type was proposed in the late 1990s in RFC 2782. …
All DNS zones begin with a Start Of Authority (SOA) record. The SOA record states that authority for a zone is starting at a particular point in the global tree of DNS names. For example, when creating a new DNS zone for ohmcar.org (a fictitious electric car company) then the process of zone creation would include the …
The AAAA DNS record type was created to hold IPv6 addresses. AAAA records, pronounced “quad A records” are similar to A records. They hold a 128-bit IPv6 address instead of a 32-bit IPv4 address. IPv6 did not exist when the original DNS specifications (RFC 1034 and 1035) were written. Only a few years later, IPv6 was created …
The A or “address” DNS record type was created to hold IPv4 addresses. Translating names to addresses is one of the most fundamental uses of the DNS! The A record type was introduced in the original DNS specifications (RFC 1034 and 1035) in 1987. Each type A record holds an IPv4 address. IPv6 did not yet exist …
The TXT or “descriptive text” DNS record type was created to hold human-readable text. It now plays a critical role in the prevention of spam on the Internet. The TXT record type was introduced in the original DNS specifications (RFC 1034 and 1035) in 1987. They were to be used for notes and text created by DNS …
The MX or “mail exchange” DNS record type is critical to the delivery of email via the Simple Mail Transfer Protocol (SMTP). MX records are used to specify a list of mail servers for a domain. If MX records are not created and maintained correctly, email for the domain will not be delivered reliably or …
The CNAME or “canonical name” DNS record type is used to alias or redirect one DNS name to another DNS name. This record type was introduced in the original DNS specifications (RFC 1034 and 1035) in 1987. CNAME records have not changed much since then, but CNAME remains a powerful and useful tool in any DNS toolbox. …
