SPF, DKIM, DMARC: What They Are and Why They Matter

Email authentication helps receiving mail servers distinguish legitimate messages from forged ones and plays a central role in protecting organizations from spoofing, phishing, and impersonation attacks.

Authentication protocols exist to establish trust between sending and receiving servers. Instead of relying solely on what an email looks like to a user, these protocols allow mail providers to check technical signals in the background and decide whether a message should be delivered, flagged, or blocked. Without authentication, attackers can easily misuse trusted domain names to send fraudulent emails that appear legitimate.

Three protocols form the foundation of modern email authentication: SPF, DKIM, and DMARC, helping organizations protect their domains, improve email trust, and reduce the risk of email-based attacks.

What are SPF, DKIM, and DMARC?

SPF, DKIM, and DMARC are the three main email authentication protocols. Together SPF, DMARC and DKIM prevent unauthorized sources from using your domain to send fraudulent emails to your prospects, clients, employees, third-party vendors, stakeholders, etc. SPF and DKIM help demonstrate the email’s legitimacy while DMARC instructs the receiver’s email server on what to do with emails failing authentication checks.

• Sender Policy Framework (SPF): Verifies the IP address of the sender to ensure it is authorized to send emails on behalf of your domain.
• Domain Keys Identified Mail (DKIM): Adds a digital signature to emails, verifying the sender’s identity and preventing message tampering.
• Domain-based Message Authentication, Reporting, and Conformance (DMARC): Provides a policy framework for enforcing SPF and DKIM checks and generating reports on email authentication results.

The Role of SPF, DKIM, and DMARC

Email authentication is important for protecting your brand against email-based cyberattacks attempted using phishing and impersonation techniques. Email authentication primarily relies on SPF, DKIM and DMARC protocols, along with additional protocols like MTA-STS, BIMI and ARC that can enhance your security even more! Here’s why you need to implement them:

• They ensure your domain name can’t be forged and misused.
• They help you prevent phishing, spamming, ransomware attacks, etc. planned and attempted in your business’s name.
• They improve your domain’s email deliverability rate. A poor email deliverability rate impacts internal communication, marketing and PR campaigns, customer retention rate, etc.

Simplify Email Authentication with PowerDMARC!

Where Can You Perform an SPF, DKIM, and DMARC Check?

SPF, DKIM, and DMARC checks can be made by verifying that the records are stored in your Domain Name System or DNS. The DNS is popularly termed as the internet’s phonebook converting domain names to their corresponding IP addresses. The DNS is used as a database for storing your domain’s information in the form of DNS records. 

An SPF, DKIM, and DMARC check is used to review existing DNS records that you can publish and store in your DNS. During email authentication checks, receiving MTAs query your DNS to lookup these records and take action based on the instructions or information defined in them.  You can use PowerDMARC’s free SPF record checker, DKIM record checker, and DMARC record checker to instantly see if your DNS contains these records!

How to Set Up SPF, DKIM and DMARC?

Follow these instructions to set up SPF, DKIM and DMARC to protect your domain and emails.

1. Create an SPF DNS record.
2. Create your DKIM public key.
3. Create your DMARC policy record and enable DMARC reporting
4. Set up dedicated mailbox to receive your DMARC reports or use a DMARC report analyzer platform.
5. Publish your SPF, DKIM and DMARC records in the DNS

What Is SPF?

Sender Policy Framework or SPF is an email authentication protocol where domain owners enlist all the servers allowed to send emails using their domain. This is done by creating a TXT SPF record that is published on the DNS. If a sending IP is not on the list, authentication fails, and the email maybe marked as spam or suspicious. However, SPF has a few limitations; it breaks when a message is forwarded or the 10 DNS lookup limit is exceeded.

If you already have an SPF record, you can use our SPF record checker to ensure it’s error-free. 

Setting up SPF 

1. Identify all your email sending sources (including third-party vendors).
2. Create an SPF record using a free SPF generator tool. The record should authorize all your sending sources.
3. Copy the record syntax.
4. Login to your DNS management console.
5. .paste the record in your DNS records section under “TXT” resource type.

Wait for a few hours for the changes to be implemented. Once done, you can use our SPF record lookup tool to ensure an error-free record.

Common challenges with SPF

When learning the challenges with SPF, DKIM, and DMARC it is worth noting there are a few common challenges domain owners face specifically with SPF implementation. They are as follows: 

• Exceeding the DNS lookup limit of 10 breaks SPF
• Exceeding the void lookup limit of 2 can break SPF
• SPF records have a 255 character length limit 
• SPF fails fo forwarded messages 

To resolve these errors, SPF records should be optimized with Macros to stay under the defined limits. Combining SPF with DKIM and DMARC also ensures smoother authentication and deliverability. 

What Is DKIM?

DomainKeys Identified Mail or DKIM lets domain owners automatically sign emails sent from their domain. DKIM works is ways similar to how you sign bank checks to validate their authenticity. DKIM signatures ensure your email content remains secure and unchanged during the delivery process.

It proceeds by storing a public key in a DKIM DNS record. The receiving mail server can access this record to get the public key. On the other hand, there’s a private key secretly stored by the sender who signs the email header with it. Receiving mail servers verify the sender’s private key by comparing it with the easily accessible public key.

Setting up DKIM 

1. You can easily set up DKIM by generating a DKIM record using PowerDMARC’s free DKIM record generator. 
2. Enter your domain name in the toolbox and click on the Generate DKIM record button. 
3. You will get a pair of private and public DKIM keys. 
4. Publish the public key on your domain’s DNS.
5. Configure your mail server to use the DKIM private key to sign the headers of all outgoing emails. This signing process adds a DKIM signature to each email, which recipients’ mail servers will verify using the corresponding DKIM public key published in your DNS. Make sure you keep your private key safe and not publish it publicly or disclose it. 

Finally, verify your DKIM public key using a DKIM lookup tool to ensure that it is correct. 

Benefits of DKIM

When looking at adding  SPF, DKIM, and DMARC authentification, DKIM specifically has several benefits in email authentication including:

• DKIM authenticates forwarded messages properly in most cases. 
• DKIM prevents cyber attackers from altering email content.
• DKIM allows each domain to manage its own public-private key pairs independently, giving organizations more granular control over their email security.

How SPF, DKIM, and DMARC Work Together

SPF, DKIM, and DMARC are designed to work as a coordinated system (rather than as standalone protections). While each protocol addresses a different part of the email authentication process, together they provide a more complete and reliable way to verify legitimate email and block impersonation attempts.

SPF focuses on the sending infrastructure by confirming that an email is coming from an authorized server. DKIM protects the message itself by verifying that the content has not been altered during delivery. DMARC brings these checks together by defining how receiving mail servers should evaluate SPF and DKIM results and what action to take when authentication fails. It also adds visibility through reporting, allowing domain owners to monitor authentication outcomes across their email traffic.

When all three protocols are properly aligned, they’re working toward the same goal: building trust between sending and receiving servers. That shared foundation closes the gaps that attackers often take advantage of when only one or two checks are in place, making spoofing and phishing much harder to pull off.

For mailbox providers, this alignment also makes their job easier. They get clearer, more consistent signals about which messages are legitimate, which leads to better filtering decisions and more reliable delivery for the emails that should be trusted.

Using SPF, DKIM, and DMARC together also supports better inbox placement. Authenticated emails are more likely to be delivered as intended rather than flagged or blocked, which helps maintain consistent communication with customers, employees, and partners. Over time, this consistency reinforces brand trust, as recipients see fewer fraudulent messages misusing your domain and more reliable delivery of legitimate email.

Common Mistakes to Avoid

Even well-intentioned email authentication setups can fall short when key details are overlooked. Small configuration issues or a lack of follow-up can weaken SPF, DKIM, and DMARC over time, leaving domains exposed to spoofing and delivery problems. Being aware of these common mistakes helps ensure your authentication strategy remains effective and resilient.

Overly long SPF records

SPF records can become too complex as organizations add more sending services over time. Excessive mechanisms and nested include statements increase DNS lookups and can exceed protocol limits, causing legitimate emails to fail SPF checks. 

Regularly reviewing which senders are authorized, clearing out services you no longer use, and tightening up the record’s structure all help keep SPF checks consistent and reliable over time.

Missing DKIM records or infrequent key rotation

When DKIM records are missing, receiving servers have no way to verify that a message hasn’t been altered, which leaves authentication incomplete even if other checks pass. And when DKIM keys aren’t rotated often enough, security slowly weakens, extending the lifespan of cryptographic keys and giving attackers more time to exploit them.

Making sure DKIM is enabled for every active sending domain and rotating keys on a regular schedule closes those gaps. It strengthens message integrity, tightens authentication, and reduces long-term risk in a way that’s easy to overlook until something goes wrong.

DMARC policies left at “none” for too long

A DMARC policy set to p=none only monitors email traffic and does not block or quarantine unauthenticated messages. While useful during initial deployment, leaving this policy unchanged delays real protection. 

Gradually moving to p=quarantine and then p=reject allows domain owners to actively prevent spoofing once authentication data has been reviewed.

Lack of monitoring of authentication reports

Failing to review DMARC reports limits visibility into how emails are being authenticated and where failures occur. Without monitoring, misconfigurations and unauthorized sending sources may go unnoticed. 

Regular analysis of reports helps identify issues early and ensures SPF, DKIM, and DMARC remain aligned with current email activity.

Wrapping Up

Once you have set up these security protocols for your domain, you need to start monitoring your reports to notice suspicious activities. By properly configuring and managing these protocols, you can significantly improve your domain security and deliverability. 

Remember, together these authentication protocols can reduce the risk of phishing, but they don’t shield against all email-based cybercrime. Thus, it’s important to follow it up with employee education and awareness.

To make monitoring, reporting, and ongoing optimization easier, PowerDMARC brings SPF, DKIM, and DMARC management into a single platform. With real-time visibility, guided policy enforcement, and automated insights, it takes a lot of the manual effort out of the process, helping teams maintain a secure, reliable email authentication setup.

Start a free 15-day trial or book a demo to strengthen your domain protection and keep your email communications trusted.

Frequently Asked Questions (FAQs)

What happens if I only set up SPF and skip DKIM or DMARC?

Setting up SPF on its own only gets you part of the way there. It can verify whether a sending server is authorized, but it doesn’t protect the visible “From” address or stop a message from being altered in transit. Without DKIM and DMARC in place, spoofed emails can still slip into inboxes, and receiving servers are left without clear instructions on what to do when authentication fails.

That’s why these protocols are meant to work together. When SPF, DKIM, and DMARC are all aligned, you get stronger, more reliable protection.

Do SPF, DKIM, or DMARC affect how my emails look to recipients?

No. These protocols work behind the scenes and do not change the appearance, content, or layout of your emails. Recipients will not see SPF, DKIM, or DMARC results directly. However, properly authenticated emails are less likely to be marked as spam, which improves inbox placement and overall trust.

How often should I review or update my SPF, DKIM, and DMARC records?

You should review your records whenever you add or remove email-sending services and as part of regular maintenance. SPF records often need updates when new tools or vendors are introduced. DKIM keys should be rotated periodically for security. DMARC reports should be reviewed consistently to detect issues early and guide policy enforcement.

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Ahona Rudra

Domain & Email Security Expert at PowerDMARC

Ahona is the Marketing Manager at PowerDMARC, with 5+ years of experience in writing about cybersecurity topics, specializing in domain and email security. Ahona holds a post-graduation degree in Journalism and Communications, solidifying her career in the security sector since 2019.

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