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Learn What SPF, DKIM, and DMARC are to Ensure Email Security for Your Domain in 2023

Email authentication is becoming increasingly vital for email deliverability. SPF, DKIM, and DMARC are the three primary authentication methods used by ISPs to verify that an email received is from a legitimate source. This article will explain how SPF, DKIM, and DMARC work and how ISPs support them.

It is vital to prevent individuals from emailing your domain address without authorization. SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) are three well-known email authentication methods. They help ISPs, and email services confirm that a particular sender is legitimately authorized to send emails from a specific domain. These techniques verify whether emails are being sent through the proper source server.

Taking proactive steps will help ensure that unauthorized emails are not sent in your name. Verifying your account with these parameters will ensure that the server on the receiving end recognizes you as a valid sender. You can adjust these settings easily in the domain panel by adding TXT records to the domain DNS (Domain Name System).

The article will discuss setting up and configuring these protocols to ensure your emails are correctly authenticated and delivered to the inbox without fail. The working of each authentication mechanism varies depending on the goal it tries to accomplish. The discussion will explore such differences among these validation processes in their operations.

Sender Policy Framework (SPF)

Sender Policy Framework is a form of authentication designating the IPs permitted to send emails from a given domain. Domain owners can establish SPF by adding a file or record on the server, allowing receiving servers to identify which domains are approved for sending an email.

Sender Policy Framework
  • Installation: It requires a text (TXT) record set in the domain’s DNS (Domain Name System) that includes a list of valid IP addresses for servers authorized to send emails through the domain.
  • Structure: The following is how a typical SPF record looks:

v=spf1 include:52223555.domain.com ~all

  • Authentication Mechanism: Every email that is sent contains a Return-path header. The return path indicates the email address to which delivery notifications regarding bounces and spam are sent. The domain of the sending server’s domain path is identified, and its DNS record information is retrieved. If the email server IP found in the SPF record matches it, then the SPF validation will be successful.

DKIM (DomainKeys Identified Mail)

DKIM is a method of authentication like SPF but more robust as it uses cryptography involving a pair of public/private keys instead of IP addresses for email authentication. It ensures that emails are not tampered with or altered en route from one server to another, allowing for precise identification of the sender at the receiving end.

  • Installation: You must generate a public key and specify the associated private key. You must set the public key hash in the TXT record and enable email signing for sending email signatures using the private key.
  • Structure: The structures of DKIM with the public key and private key are as given in the following examples:
  1. DKIM record in DNS with a public key


  1. DKIM signature in the email with a private key:

DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; s=fnc; d=env.mymail.com; h=To:From:Reply-To:Subject:Message-ID:List-Unsubscribe:MIME-Version:Content-Type:Content-Transfer-Encoding:List-Unsubscribe:Date;

bh=DRRFSFDSFWERRfdfgdsgeERFSFMps774=; b=oDQdtCY85ckhjSDFSDFEdsfsdfdsfasedf9+sVkuMD5bpevJB4SB3+HEP0pikyDQpeLEWOeC2rwyrhDucDYctVYRr6DSFDFEghghdfdsfasedf9+s


  • Authentication Mechanism:  As mentioned above, DKIM involves the generation of a public key and a private key. The private key stored on the email server helps encrypt the signature added as a header in each email sent from the server. This encryption ensures the security of the signature. You can confirm the sender’s legitimacy by decrypting and authenticating the signature.

DMARC (Domain-based Message Authentication, Reporting, and Conformance)

DMARC is a tool that builds on SPF and DKIM to authenticate emails further. Thus, you must activate a DMARC record in conjunction with these two records for optimal security.

implement DMARC

To implement DMARC, you must configure SPF and DKIM records first. Then, configure the DMARC settings in the TXT records of your domain’s DNS settings. By comparing the validity of SPF and DKIM records, DMARC enables users to set policies and receive generated reports for failed validation.

  • Structure: The following is the typical structure of a DMARC record:

_dmarc.yourdomain.com. IN TXT “v=DMARC1\; p=none\; rua=mailto:dmarc-aggregate@yourdomain.com\; ruf=mailto:dmarc-afrf@yourdomain.com\; pct=100”

  • Installation: You can add a DMARC record directly to the DNS TXT record to improve the security of emails sent from your domain. Ensure SPF and DKIM records are set in the DNS already.
  • Authentication Mechanism: When the recipient server receives an email, it verifies the DMARC record to ensure its legitimacy. Since DMARC will work in conjunction with SPF and DKIM, it will check the IP validation of SPF and the signature of the DKIM. It will help decide further action with failed authentication and help generate reports for such emails.

How Do ISPs Use SPF, DKIM, and DMARC?

Internet Service Providers (ISPs) use a combination of SPF, DKIM, and DMARC to help protect users from unwanted emails, cyber threats, and fraud, such as spam, email spoofing, and phishing attempts.

To summarize the three protocols, SPF is a mechanism that verifies that the sender of an email is who they say they are by checking the sender’s IP address against the addresses listed in the DNS record of the sender’s domain.

On the other hand, DKIM is a protocol that uses cryptographic authentication to verify that an email has not been modified in transit and ensure that it indeed originates from the domain listed in the ‘From’ field. DMARC uses the combined efforts of SPF and DKIM to verify that emails are being sent from the claimed sender’s domain and not from an impostor. In addition, it can generate reports concerning failed authentications.

Final Words

Email authentication can be a tricky process. A deeper understanding of the three prominent types of email authentication – SPF, DKIM, and DMARC – can help you with reliable email authentication.

domain reputation

Knowing how each works and how they work together will help protect your domain’s reputation and prevent unwanted senders who impersonate a genuine address. Once you understand the three protocols, it is easy for you to arm yourselves with the right tools to ensure that your emails reach the correct recipients without fail.

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