The Structure Of SPF Syntax With Tags

SPF Syntax Structure

Any typical SPF record example includes tags such as the ones listed below:

• a: This tag helps one validate the IP address that the sender has used to send an email from their domain. If it matches the sender’s IP address completely, one can rest assured that it is authentic.
• mx: Like the previous mechanism, this too authenticates the IP address of the client who has sent the mail. If it locates the IP address of the sender within the records, it is safe.
• ip6 and ip4: These mechanisms specify the IPv6 and the IPv4 IP addresses, respectively, that can send emails for the domain.
• ptr: This mechanism is not recommended as per the RFC 7208 guidelines. Its function is to make sure that a minimum of one PTR hostname found in the A record finds an exact match with that of the IP of the sender/ client.
• exists: This tag runs an ‘A’ record search on the mentioned domain. Its function is to verify the existence of an ‘A’ record.
• ~all: This mechanism is typically found at the end of the SPF record. SPF ~all has been designed to provide the user or the email receiver with proper advice regarding what steps they can take if there is no such exact match with the SPF record syntax. The term “~all” suggests that the email should be treated as suspicious. Hence, it facilitates the acceptance of the message but flags it to treat it with caution.

The SPF tags mentioned above constitute SPF records and can be automatically created using SPF generator tools. They are of utmost importance to the receiver of the emails since they can verify whether or not the emails are from safe sources. SPF is one of the oldest and one of the most reliable authentication tools (An SPF record can also be tested using an SPF Validator, which automatically tests it for anomalies). This protection can be further strengthened by adding two further layers, namely the DKIM and the DMARC tools, which were later created following in the footsteps of SPF.