Imagine this: It’s that time of day where you open your email marketing platform’s dashboard to check the numbers. You see your open rates are unexpectedly low. Some recipients report that your emails landed in their spam folders—or worse, never arrived at all.
Picture this: You open the dashboard of your email marketing platform and take a look at the numbers. And then you notice your open rates are lower than you would have hoped. Some recipients even say your emails got sent to spam—or even worse, never arrived. You run an email deliverability test and see your spam rates shooting up.
You begin to wonder: Is my email system busted? Am I being blocked?
Among the leading causes for this frustration is an error in email authentication. Without robust authentication, internet service providers (ISPs) and email providers have no way of knowing if your email is really from you. This could expose your domain to spoofing, phishing and deliverability problems.
However, even legitimate senders and emails can get blocked or rerouted to spam end up blocked or diverted to spam if these authentication protocols aren’t configured as they should be. That’s why you want your bases covered, so you can make sure your emails land in inboxes.
Understanding email authentication protocols
Email authentication is the mechanism that checks if an email does, in fact, originate from the sender or domain it says to be. It’s akin to a security check for your messages, intended to protect senders and recipients alike.
When you send an email, it goes through a bunch of email servers before it lands in the recipient’s inbox. With no authentication, bad actors can fake sending emails from your domain (spoofing). Spoofed emails ruin your brand, frustrate your customers, and can cause your real emails to be flagged as spam.
Just to emphasize the importance of authentication in the battle against email spoofing and phishing attacks, check out these numbers:
- An estimate of 3.4 billion emails a day are sent by cybercriminals and these are designed to look like they come from trusted senders.
- Google blocks an estimate of 100 million phishing emails per day.
- The average cost of a business data breach is more than $4 million.
Authentication protocols make it possible for ISPs and email providers to verify that your emails really are your emails, and that you are who you say you are. They examine the individual records posted on your domain’s DNS (Domain Name System) to confirm senders and message legitimacy.
The three main protocols you need to know are:
- SPF (Sender Policy Framework): Informs servers receiving your email whom you have allowed to send on behalf of your domain
- DKIM (DomainKeys Identified Mail): Attaches a digital signature to each email to verify it hasn’t been tampered with en route
- DMARC (Domain-based Message Authentication, Reporting & Conformance): Connects SPF and DKIM and tells or instructs the receiving server what to do should an en email fails to pass authentication checks
Together, these protocols form the foundation of modern email security.
🔖 Related Reading: SPF, DKIM, and DMARC: Boosting Email Security and Deliverability
What is SPF (Sender Policy Framework)?
SPF, or Sender Policy Framework, is an email authentication protocol that helps identify which mail servers are permitted to send emails on behalf of your domain.
Think of SPF as a guest list for your email domain—only the servers on this list are actually permitted to send emails from your domain.
The main purpose of implementing SPF is to prevent spoofing. Spoofed emails damage your brand’s reputation, confuse your customers, and can result in legitimate emails being marked as spam.
How SPF works
When you send an email messages, the recipient mail server verifies the SPF record published in your domain DNS. This record contains the IP addresses or hostnames of servers allowed to send emails for your domain, which then help prevent email spoofing.
Here’s the step-by-step process:
- The receiving server receives an email claiming to be from your domain.
- The server will proceed to checking the SPF record in DNS.
- It compares the sender’s IP address against the authorized list in your SPF record.
- If the IP matches an authorized server, the email has passed SPF. The recipient server treats the email as more trustworthy and is more likely to deliver it to the inbox.
- If the IP is not listed, the SPF check fails, signaling possible spoofing. Emails that fail SPF mean the server may mark the email as spam, reject it outright, or apply other policies based on DMARC rules. This reduces the chance your message reaches the recipient.
Common SPF setup challenges
- Incorrect syntax: Just one typo can render the entire SPF record unusable, causing legitimate emails to fail checks.
- Missing authorized servers: Forgetting to include third-party services (like email marketing platforms or CRMs) can cause their emails to fail SPF.
- Too many DNS lookups: An SPF check only permits a maximum of 10 lookups in DNS. If your record includes many external services, you may hit this limit, causing SPF to fail. To avoid hitting the limit, consider using SPF flattening tools to simplify your records.
🔖 Related Reading: The Definitive Guide to SPF in Email
What is DKIM (DomainKeys Identified Mail)?
An email authentication system called DKIM essentially attaches a digital signature to outgoing emails, and is widely used. How is it different from SPF?
- SPF authenticates the sending server
- DKIM ensures that the content of your email hasn’t been tampered with during transit.
It allows the recipient to verify that the email was really sent from your domain and wasn’t modified after you sent it. This establishes confidence for both email providers and subscribers, safeguarding your brand reputation and increasing deliverability.
How DKIM key works
DKIM is based on a pair of cryptographic keys—one private and one public:
- Your mail server uses a private key to sign an outgoing email with a unique digital signature.
- The recipient’s mail server looks up the DKIM public key that you published in your domain’s DNS records and uses it to check the signature.
If the signature matches and verifies correctly, it means the email is authentic and unaltered.
What DKIM signatures look like
DKIM adds a field in the email header that looks like:
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yourdomain.com; s=selector1; …
The d= tag specifies the signing domain, and the s= tag identifies the selector used to find the public key in DNS.
Common DKIM setup challenges
- Generating keys: The process for generating and taking care of your public/private key-pair can be intimidating for new users.
- DNS record configuration: Adding the right public key in the form of a TXT record to DNS needs to be precise.
- Key rotation: Regularly updating keys (key rotation) is important for security but can lead to signature failures if not handled incorrectly.
- Selector management: Using more than one selector to manage keys in the different servers or services can be
🔖 Additional resources:
- What is DKIM? How to set it?
- How to Set Up DKIM for Google Workspace
- Everything You Need to Know About DKIM Selector: What Is It and How to Find It?
What is DMARC (Domain-based Message Authentication, Reporting, and Conformance)?
DMARC builds on SPF and DKIM to describe how mail receivers should handle unauthenticated mail. It’s a policy that is sent with an email that tells receiving servers how to act with an email if SPF and DKIM checks pass or fail.
DMARC provides reports that can tell you which IP addresses are sending mail on your behalf, whether the authentication passed or failed, and if someone is trying to send mail using your domain without permission. This information should be used by you to determine misconfigurations, unauthorized senders, or phishing attacks so you may take appropriate action.
In simple terms, a DMARC allows domain owners to protect your domain from spoofing and phishing by enforcing authentication and offering insights into your email traffic.
How DMARC works
DMARC essentially involves publishing a DNS TXT record that includes:
- The policy to apply when emails fail authentication (none, quarantine, or reject)
- Where to send reports about authentication results
- Optional settings like alignment requirements for SPF and DKIM
Policy options explained:
- none: No processing is performed on failed emails, just reports. Helpful for surveillance prior to implementation
- quarantine: Messages that don’t pass checks are identified as suspicious and frequently sent to spam folders
- reject: Emails failing DMARC are rejected outright by the receiving server
Receiving servers check incoming emails against the domain’s DMARC policies. Based on the policy and results of SPF and DKIM, they decide whether to deliver, quarantine, or reject the message.
Common DMARC setup challenges
- Policy enforcement: Moving too quickly to strict policies (quarantine/reject) can cause legitimate emails to be blocked if SPF/DKIM aren’t properly aligned.
- Report management: DMARC reports are technical and voluminous, requiring tools or expertise to analyze effectively.
- Alignment configuration: Ensuring SPF and DKIM alignment (matching the domain in the “From” header) is crucial but can be complex.
How SPF, DKIM, and DMARC work together to improve email security
SPF, DKIM, and DMARC are the three pillars of email authentication. They are not standalone solutions—they form a powerful trio that works together to secure your email, avoid email spoofing, and improve deliverability.
When all three protocols are properly set up, here’s what happens:
- Your emails are significantly less likely to be considered spam or bounced.
- You secure your domain against spoofing and phishing attacks.
- ISPs and recipients are convinced that you and your email are trustworthy.
- Your brand’s reputation is still good and your email campaigns land in more inboxes.
How Warmy.io simplifies email authentication
Setting up and managing SPF, DKIM, and DMARC can be complex, especially if you’re not a technical expert. That’s why Warmy.io offers an integrated suite of tools designed to make email authentication straightforward and hassle-free.
Authentication monitoring and tracking
Warmy’s free email deliverability test is recommended for senders who want to get an idea on their inbox placement currently. It can quickly check if your emails are landing on its intended recipient and shows the percentage of emails that ends in spam, promotions, inbox, and unreceived across major email providers. By taking this test, senders can get an idea of where they stand and what factors are affecting their deliverability.
Combined with the Domain Health Hub, senders can have access to these insights:
- Comprehensive DNS status checks to easily validate SPF, DKIM, DMARC, rDNS, MX, and A records for stronger authentication & security.
- Learn if your domain or IP is listed on any blacklists so you can proceed with the delisting process.
- Authentication verification: Assess your email reputation and verifies your email authentication settings such as SPF, DKIM, and DMARC.
- A domain health score based on factors like authentication, blacklist status, and inbox placement tests.
- Weekly or monthly tracking of deliverability metrics
Free tools for setting up your SPF and DMARC records
Warmy’s Free SPF Record Generator helps with:
- Automatically generating the correct SPF record based on your email service providers.
- Optimizing SPF structure to prevent lookup failures.
- Ensuring compliance with best practices to avoid SPF misconfigurations.
Meanwhile, Warmy.io’s Free DMARC Record Generator helps:
- Create a valid DMARC record based on your email security needs.
- Monitor authentication failures to detect unauthorized senders.
- Gradually enforce DMARC policies to prevent email rejections.
Secure deliverability beyond authentication with Warmy
Of course, authentication issues aren’t the only factors that affect deliverability. Email deliverability, as you know, is multi-layered. Getting your SPF, DKIM, and DMARC records perfect is not a 100% guarantee your emails will get through to the inbox. There are other players, and Warmy, as an all-in-one deliverability tool provides solutions to cover all angles.
AI-powered warmup
Warmy’s AI-powered email warmup gradually builds your sender reputation by automatically sending and receiving real emails with trusted inboxes. This natural interaction trains email providers to recognize your domain as legitimate and trustworthy, reducing the risk of your messages being marked as spam. The AI continuously adjusts sending patterns based on your mailbox health, optimizing the warmup process without manual intervention.
With the new Warmup Preferences feature, senders can also customize how the warmup is distributed across specific providers—further adding to the personalized experience.
🔖 Related Reading: Mastering Email Deliverability: The Modern Guide to Authentication and Inbox Warm-Up is a report from the Warmy Research Team that brings clarity to how authentication and warmup work together.
Advanced seed lists
Warmy offers seed lists which are collections of genuine email addresses across various providers that you can use to test your campaigns before launching while improving the quality of your warm-up too. By sending emails to these seed addresses, you can monitor inbox placement and spot any deliverability issues early. This proactive approach helps catch potential problems before they affect your real audience.
Template checker (now with Chrome extension!)
A clean, error-free email template is critical for inbox placement and engagement. Warmy’s Template Checker scans your email content for errors, spam trigger words, formatting issues, and rendering problems across devices. By catching these issues early, you ensure your emails comply with best practices and avoid spam filters even before you hit ‘Send.’ Now with its Chrome extension, getting feedback and tweaking your email is even more seamless.
Take control of your email deliverability today
Email authentication with SPF, DKIM, and DMARC is no longer optional—it’s a necessity to protect your brand, secure your domain, and improve deliverability.
But authentication is just one part. Combining it with Warmy’s other features ensures your campaigns not only pass technical checks but also reach and engage your audience effectively.
Sign up now at Warmy.io and protect your domain while maximizing your email marketing success.
