Email Authentication: How to Authenticate Your Email with DMARC, DKIM, and SPF

Email is widely used by every organization to communicate with employees, potential customers, and business partners. Since its inception, email communication has always had security issues, and sadly, simple message encryption between email servers isn’t enough to keep the bad guys out. 

Cybercriminals are getting more dangerous, and email is one of the most popular attack vectors. Phishing scams, spoofing, and spamming are a few of the many cyberattacks where email is the main entry point. Hackers trick their victims by forging messages that appear to come from legitimate sources.

For that reason, most organizations follow stringent email security practices to mitigate these risks. One of the best approaches is to authenticate your email messages properly. 

When we talk about email authentication, we’re talking about SPF, DKIM, and DMARC, which help to validate the authenticity of an email. Aside from safeguarding your domain from cyber actors, these protocols help to improve your deliverability rates. 

This article discusses how you can authenticate your email with DMARC, DKIM, and SPF.

What Comes Before DMARC?

Even though DMARC is at the top layer of your email security protocol, it can’t stand on its own. Before implementing DMARC, you must first deploy SPF and DKIM, the two primary authentication protocols. SPF and DKIM use different approaches to validate that an email message comes from a legitimate source. 

The DMARC email authentication protocol was designed to complement and enhance SPF and DKIM, reinforcing their strengths while also addressing their shortcomings. Now that we’ve given you a quick overview of these valuable email standards let’s discuss how they work for email authentication. 

How SPF Contributes to Email Authentication?

SPF, or Sender Policy Framework, is an email authentication protocol that allows a domain owner to list all the IP addresses authorized to send messages on their behalf. When an email is sent, the receiving server checks whether the associated domain has an SPF record and acts accordingly. 

If the sender’s IP address isn’t listed in the SPF record, the email fails SPF authentication and is either rejected or sent to the spam folder. This means scammers, spammers, and fraudsters can’t spoof your company’s domain for nefarious purposes. 

Implementing SPF also signals to email service providers that you’re serious about email security and that your domain is legitimate, which can improve deliverability rates. 

However, SPF has a few limitations, which cause some security concerns. Emails automatically fail authentication when forwarded by someone else since those IP addresses aren’t listed in the SPF record.

The ‘10 DNS lookup’ error is also a common issue, but our EasySPF tool can help. Perhaps more importantly, SPF doesn’t protect a domain from hackers that can spoof the visible “from:” address or display name. 

What Does DKIM Do for Email Authentication?

DomainKeys Identified Mail (DKIM) is an email authentication protocol that uses public cryptography to digitally sign every message so that the receiving mail server can verify the sender and the authenticity of the email. The standard uses cryptographic authentication to validate a domain associated with a message. 

DKIM provides email authentication using an encrypted key pair. One key is private, used to add a digital DKIM signature to each email. The other key is public, used by receiving mail servers to confirm the authenticity and source of an email, and to identify whether it was modified during transit. 

Though DKIM offers a way for mail receivers to verify a sender and validate a message, it doesn’t stop bad actors from using a reputable domain and DKIM signing to send malicious emails. Moreover, DKIM only considers some (not all) parts of a message during verification so cyberattackers can add malware-loaded headers that bypass DKIM authentication. 

Lastly, like SPF, DKIM doesn’t allow domain owners to instruct receiving servers on handling failed authentication messages. (Use our free DKIM Validator tool).

How Do SPF and DKIM Come Together in DMARC?

Before we answer the above question, let’s answer this: How does DMARC work? DMARC is an anti-spoofing authentication protocol that leverages DKIM and SPF to strengthen your domain’s email security. You must publish these three email protocols as TXT records in your DNS settings. For DKIM, you need an additional configuration in the email gateway. 

That said, it’s a rather technical process that can’t be rushed or you’ll risk authentication errors and legitimate emails being rejected. For many, SPF is the first step toward DMARC compliance followed by DKIM, both requiring proper configuration, authentication, and alignment.

Here’s a rundown of how email authentication works once you have DMARC compliance through proper DMARC, SPF, and DKIM deployment. When you send an email to a recipient, the receiving email server performs different queries in the DNS as follows:

• SPF authentication – It checks if the email comes from an IP address authorized to send a message on the domain’s behalf. 

• DKIM authentication – It also confirms if the sender is authorized and the email wasn’t altered in transit by verifying the digital DKIM signature.

• DMARC policy and alignment – The DMARC policy and alignment further validates SPF and DKIM authentication. It matches the “From:” address to the return-path address (for SPF) and the “d=” domain in the DKIM header. The  DMARC policy is applied based on this result.
• If the message fails SPF and DKIM authentication, the DMARC policy is implemented based on your deployment.  Note that there are three central DMARC policies that you can implement: None, Quarantine, and Reject.
• If the email passes the authentication checks, then the message lands in the recipient’s inbox. 

Once the receiving email server has applied the required DMARC policy, it sends a DMARC report to the address assigned by the email sender. When adding a DMARC record to your DNS, you’ll be asked to indicate the email address where you want the report to land. DMARC aggregate reports encompass the following:

• The number of emails sent to the recipient from your domain.
• The IP addresses that send messages on your domain’s behalf.
• The status of the SPF and DKIM authentication checks.
• The policy implemented on your emails.

You can check or validate your DMARC record using our free DMARC Record Checker.

What Lies Beyond DMARC?

As vital as the Domain-based Message Authentication, Reporting, and Conformance (DMARC) is to safeguard your email from spoofing and other phishing attempts, it may not suffice on its own in the near future.

Cyberattacks are getting more sophisticated, and you’ll need more than DMARC to protect your organization’s domain. Also, email phishing remains one of the most effective methods hackers use to trick users and compromise sensitive information. So DMARC is just the beginning. 

There are other measures you can already put into place to make your email more secure. One such measure is Brand Indicator for Message Identification (BIMI). It’s an email specification that works alongside SPF, DKIM, and DMARC to confirm that you are who you claim to be. 

With BIMI, you can show your brand logo beside the emails sent to your recipients. It provides a visual clue that tells the receiver your email has been authenticated. However, for BIMI to work, your email must pass both SPF and DKIM authentication checks, with your DMARC policy set to either quarantine or reject. 

If you don’t know the status of your BIMI record, you can use our BIMI Record Checker to look up and validate your BIMI configuration. 

Business Email Compromise attacks are on the rise and can be challenging to defend against. In this case, organizations should ensure they educate their employees to follow best email security practices.

Final Thoughts

The email attack landscape is evolving, so the need to authenticate your emails with SPF, DKIM and DMARC can’t be underestimated. These protocols protect your domain from BEC attacks, email spoofing, and other phishing attacks. 

Aside from this, implementing these protocols will nurture trust in your brand from customers, vendors, and business partners. 

You can use our DMARC Record Lookup tool to determine whether your email authentication protocols are in place. If not, we’ll help you implement SPF, DKIM, and DMARC, as well as BIMI. Contact us today!