Introduction To Email Authentication
Aug 8, 2020
Guide Takeaways
Email authentication verifies that emails truly come from the domain they claim, protecting users from phishing and spoofing.
SPF, DKIM, and DMARC work together to define who can send mail for a domain, validate authenticity, and enforce policies.
Without authentication, cybercriminals can impersonate your brand and trick users into giving away sensitive information.
Proper authentication significantly improves deliverability by increasing trust with receiving mail servers.
SaaS products rely heavily on email; authentication is essential to ensure notifications, alerts, and onboarding emails reach users reliably.
SPF defines sending servers, DKIM signs messages, and DMARC combines both to tell receivers what to do if checks fail.
Email authentication protects brand reputation, prevents domain misuse, and builds trust with customers.
Implementing authentication is one of the highest-impact steps SaaS teams can take for security and deliverability.
Q&A Highlights
What is email authentication?
Email authentication is a framework of standards that verify whether an email truly comes from the domain it claims to be sent from. It protects users from phishing, spoofing, and fraudulent messages.
Why is email authentication important for SaaS products?
Most SaaS apps rely heavily on transactional emails. Authentication ensures these messages reach users’ inboxes, maintains trust, and prevents attackers from impersonating your product.
What problems arise without authentication?
Cybercriminals can forge your domain, send phishing emails, damage your brand reputation, and reduce deliverability—leading to users missing important product notifications.
What are SPF, DKIM, and DMARC?
SPF lists the IPs allowed to send mail for your domain.
DKIM verifies message integrity through cryptographic signatures.
DMARC combines both and defines what receivers should do when checks fail.Does email authentication stop all phishing?
It doesn’t stop attackers from sending emails—but it does stop receiving servers from trusting forged messages. This dramatically reduces the reach and impact of phishing attempts.
How does DNS relate to email authentication?
DNS acts as the public directory for SPF, DKIM, and DMARC policies. Receivers look up these DNS records to confirm authenticity before delivering messages.
Can email authentication improve deliverability?
Yes. Authentication increases trust with receiving servers, improving inbox placement and reducing the chance that legitimate emails end up in spam.
What’s the first step to setting up email authentication?
Start by publishing SPF and DKIM records for your sending domain, then configure a DMARC policy to enforce how receivers should treat unauthenticated emails.
Email authentication is a technical solution to preventing phishing and forged emails. It’s essential that SaaS product teams understand how to use email authentication to protect their apps’ email notifications. In this article, you will learn:
Email authentication is a technical solution to proving that an email is not forged. In other words, it provides a way to verify that an email comes from who it claims to be from. Email authentication is most often used to block harmful or fraudulent uses of email such as phishing and spam.
In practice, we use the term “email authentication” to refer to technical standards that make this verification possible. The most commonly used email authentication standards are SPF, DKIM, and DMARC. These standards were designed to supplement SMTP, the basic protocol used to send email, because SMTP does not itself include any authentication mechanisms.
There are several different approaches to email authentication, each with its own advantages and disadvantages. Although the specific technical implementation varies from approach to approach, in general, the process works something like this:
A business or organization that sends email establishes a policy that defines the rules by which email from its domain name can be authenticated.
The email sender configures its mail servers and other technical infrastructure to implement and publish these rules.
A mail server that receives email authenticates the messages it receives by checking details about an incoming email message against the rules defined by the domain owner.
The receiving mail server acts upon the results of this authentication to deliver, flag, or even reject the message.
As these steps make clear, in order for this process to work, the sender and the receiver both must participate. That’s why technical standards for email authentication are so important: they define a common approach to defining the rules for email authentication that any organization can implement. Bear in mind that email sender authentication provides recipients of a message some level of certainty that the email message actually originated from the represented source. This ultimately generates trust and confidence in recipients, which is why understanding how to authenticate email is crucial to organizations.
SPF, DKIM, and DMARC are all standards that enable different aspects of email authentication. They address complementary issues.
Standard | What It Does |
|---|---|
SPF | Defines which IP addresses are allowed to send email for your domain |
DKIM | Uses cryptographic signatures to verify the message wasn’t altered |
DMARC | Combines SPF + DKIM and tells receiving servers how to handle failures |
SPF allows senders to define which IP addresses are allowed to send mail for a particular domain.
DKIM provides an encryption key and digital signature that verifies that an email message was not faked or altered.
DMARC unifies the SPF and DKIM authentication mechanisms into a common framework and allows domain owners to declare how they would like email from that domain to be handled if it fails an authorization test.
These email authentication standards supplement SMTP, the basic protocol used to send email, and most modern email systems support them. All three of these standards leverage the ubiquitous domain name system (DNS) for implementation. With DNS acting as the phone book of the Web, essentially establishing the legitimacy of domains through a rigorous process of analysis and verification, sophisticated email senders leverage email domain authentication as a fundamental component of security and deliverability.
