What Are SPF Records & How They Can Be Used To Achieve Better Results In Email Deliverability For Your Domain

The Role Of SPF Records In An Email Flow

SPF’s relevance can be understood from SPF records’ role in the email traffic to ensure email deliverability at its final destination, as explained below.

• When someone sends an email from a given domain name, the server that handles it before sending it out extracts corresponding SPF records from the DNS TXT records.
• It then checks the list of IP addresses included in the SPF records authorized to send an email on behalf of the business.
• If the SPF check is validated, then the email is passed for further processing to be sent out.
• Otherwise, the email will be noted as suspicious, and a predefined set of operations will be performed upon the potentially malicious email.

Method To Create An SPF Record

As mentioned earlier, SPF records are written and implemented using the TXT record. The entire development and deployment process is explained below.

• Identifying The IP Addresses To Send Emails: First of all, identifying all the nodes connected to a domain is required. These devices can include mail servers, end-user mailbox providers, ISP, in-office mail servers, and other externally linked servers.
• Define A List Of Systems To Send Emails From The Domain: Defining the authorized and unauthorized systems allows organizations to avoid spoofing of the domain by malicious actors. If an organization sends emails from multiple domains, each of them should be separately listed.
• Setup SPF Record: Copy-paste the script, v=spf1 ip4:[IP ADDRESS] -all, into a TXT record before deployment. In the script, ‘IP ADDRESS’ is the list of authorized systems, and any other external systems can be appended using the ‘include’ keyword if required. The non-sending systems are denoted using v=spf1 -all script.
• SPF Record Deployment: The DNS administrator is responsible for uploading the SPF record to the domain as a TXT record. However, users are recommended to cross-check the assigned IP addresses before establishing them to be cyber resilient.

Limitations Of SPF Records

As per SPF policies, each name needs to have an SPF record. Also, SPF has various constraints concerning lookups and the number of items, as discussed below.

• More than ten mechanisms are not allowed for SPF records in DNS TXT record lookups.
• The mechanism ‘ptr’ should not result in querying more than ten address locations.
• Finally, SPF MX records must not query more than ten records using the MX mechanism.

Modifiers In SPF Records

Modifiers in SPF records usually appear once at the end and are name-value pairs separated using the ‘equals to’ sign ( = ) to assign information. The processing frameworks will ignore any unrecognized modifiers. Modifiers such as ‘redirect’ are used to point to another SPF record when SPF records are established across multiple domains of the same organization. Similarly, the ‘include’ mechanism is used to append third-party systems to the authorized list of senders. And, the ‘exp’ modifier is used to explain if a qualifier is in a mechanism.

The SPF record’s relevance is more in organizations where many users are assigned to communicate through emails on behalf of the organization. SPF records are predominantly used to safeguard organizations from being compromised using spoofing techniques. Since a list of sources authorized to send emails is listed in the SPF records in DNS, SPF records’ formatting requires some effort and knowledge. A systematically developed SPF record will ensure email deliverability and protect the organization from getting blacklisted by other vendors, besides maintaining brand reputation.