Guide To Mail Server Configuration

TXT (TYPE 16) or SPF (TYPE 99) Records types in DNS

Please note: SPF (TYPE 99) is now obsolete

When the standard was introduced, your SPF record was stored as a TXT record (TYPE 16). In 2005, a new standard was introduced, SPF (TYPE 99). Originally SPF was created to supersede the original TXT record. However, mail servers reverted to the original TXT record and SPF (TYPE 99) became obsolete.

Now, even though SPF (TYPE 99) is obsolete, it’s still recommended to have the records present. If your Authentication String contains both TYPE 99 and TYPE 16, you’ll be considered “SPF-Compliant”. If you only have TYPE 16, you’ll be considered “Compliant”.

DomainKeys (DKIM)

DomainKeys is a deprecated email authentication protocol developed by Yahoo. It was created to verify the message integrity from any given sender’s domain name.

DomainKeys was superseded by the DomainKeys Identified Mail (DKIM) email authentication method. Even though this standard is superseded, many mail servers (old and new) still use this standard, and if you have the option, you should implement it.