Things to Note About Email Authentication Protocols: SPF, DKIM, and DMARC

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Email marketing is vital to today’s business growth. Email is currently the most widely used marketing channel, with over 4 billion users worldwide.

Because of COVID-19, consumers are using email more than ever. This is why over 60% of consumers prefer email communication with their favorite brands.

These emails can only convert if they reach the intended recipients. Your ROI will be significantly reduced if your emails frequently bounce or end up in the spam folder.

You need a foolproof authentication strategy to ensure your emails reach your recipients every time. Learn about email authentication and how it can benefit your business.

A reminder about email deliverability and why it matters.

Email Deliverability

Email deliverability is a metric that measures how likely your email is to reach the subscriber’s inbox. Marketers value this metric because only emails that reach the inbox are opened.

Email deliverability is affected by measurable factors such as:

  • Reputation: A trustworthy domain will have fewer blocklists and spam folders.
  • Email content: ISPs look for spam-like content, unusual headers, and suspicious links in emails.
  • Authentication: SPF, DKIM, and DMARC protocols determine the authenticity of your domain and email content. We’ll get into these protocols later.

Why do you need to care about email deliverability?

Marketers frequently argue that email deliverability is irrelevant: once sent, who cares what the recipient does with it?

Wrong! This way of thinking can stifle your company’s growth.

Why prioritizing email deliverability is critical

  1. Email deliverability strengthens your brand’s reputation with email service providers (ESPs).
  2. High email deliverability companies saw a 4400% return on investment last year.
  3. Email acquires 40% more customers than Facebook and Twitter.
  4. Email deliverability can improve customer experience and loyalty.

If you don’t know how to authenticate your email, let’s start with the definition.

Email Authentication

Before sending email content through an ESP, you must verify your domain and email addresses. An email is authenticated when it passes this verification step.

Previously, businesses could buy email lists and spam random people, resulting in massive spam cases.

Anti-spam organizations and major corporations like the Anti-Spam Research Group (ASRG) and Yahoo collaborated to develop email authentication protocols.

So they created several authentication methods to protect users and businesses.

Methods of Email Authentication

The standard SMTP server only receives and sends emails without authentication. So these SMTP servers require extra authentication to ensure mail security.

The Internet Engineering Task Force (IETF) introduced email protocols to prevent spam in the early days of the internet.

We now have the following email authentication methods thanks to their hard work:

1. SPF

Authenticate the sender’s IP address and domain with SPF (Sender Policy Framework).

The SPF record contains DNS TXT records linked to a domain (or range of addresses belonging to the same network).

SPF was the first widely recognized email authentication protocol, created in the early 2000s.

Without valid SPF records, email senders are often subjected to secondary authentication. Most of them end up in spam.

Aside from spoofing and other malicious email activity, SPF authentication does not provide complete protection. When changing ISPs, you must update the records.


DKIM (DomainKeys Identified Mail) uses OpenDKIM to generate encrypted tokens required for recipient server validation.

A public and a private encryption key are used to determine whether the original content was changed during transmission.

The private key is only accessible by the domain owner and acts as a unique signature for outgoing messages.

Although DKIM is a more secure protocol than SPF, they both work well to protect the sender and receiver. Consider them an email authentication ‘two-factor verification’.


This is a process that verifies the message source and generates reports about its compliance with rules.

DMARC works with SPF or DKIM to process requests. Notify the server what to do if the source domain is not authenticated. The DNS record for DMARC actions is p-actions:

  • p=none — Nothing happens.
  • p=reject — rejects mail that fails authentication (SPF or DKIM).
  • p=quarantine — the receiving server marks the unverified email as spam.
  • v — receiving server DMARC check

DMARC can also send feedback records containing authentication status information to your preferred email address. This data helps you monitor your domain and prevent spoofing.

Why Always Begin with Authentication

Why should your company spend time and resources verifying your domain and email? Lets take a look at some points below

1. Stops phishing

Your company’s emails pass through SMTP servers before reaching the recipient. But malicious actors can attack these servers. Setting up a fake SMTP server to review and test your email campaigns is one option.

Unfortunately, phishers can use advanced mail servers to bypass standard checks.

However, if you verify your email, you will be protected.

2. Stops scammers

Scammers can use your company’s name to defraud customers or spread false news.

According to the FBI’s Internet Crime Complaint Center (IC3), over $4.2 billion was lost due to online fraud. Just the reported cases!

But how can you protect consumers?

Only email service providers authenticate users. You should also make your PTR record available to the mail provider.

So that incoming emails that don’t match your PTR record (and encryption keys) don’t reach your customers’ inboxes.

3. Improves brand reputation

Email authentication validates your brand’s domain name and email address, establishing trustworthiness. With DMARC authentication, your customers won’t get phishing emails from you. So they will trust your brand.

Because every business relies on reputation to increase sales, you must authenticate your email.

4. Sets apart your brand

According to Oberlo, 90% of marketers use email. These figures show fierce competition for consumers’ inboxes — and you don’t want to be spammed.

Thus, email authentication can set your brand apart from the crowd and enhance your reputation.

5. Enhances email delivery

Deliverability is the key.

Email authentication protocols ensure that your messages reach their intended recipients. Also, ISPs and inbox providers collect data on email engagement and delivery, which they use to calculate brand reputation and domain score.