How Email Authentication (SPF, DKIM, DMARC) Affects Deliverability

Mar 16, 2025

Phew. Have you ever sent an email to an individual who is not in his or her inbox but worse in spam? That's a real pain, isn't it? Well, this usually happens because the email authentication settings are either missing or incorrect. These settings include things like SPF, DKIM, and DMARC.

Let's keep it real so that you know how to increase your email deliverability and make sure that where your email goes, it goes there.

What is Email Authentication?

Imagine sending a letter with your name on it. However, someone else can easily copy your signature. That is precisely what happens to emails that do not have authentication. Email authentication is a way to determine if an email is indeed from you and not from someone else impersonating you in an email message.

SPF, DKIM, and DMARC: A Good and Strong Trio for Email Security

This trio of protocols ensures email security.

1. SPF: Sender Policy Framework

SPF acts as the bouncer for your domain, being the authoritative policy that defines which mail servers are permitted to send emails on behalf of your domain. If an unauthorized server attempts to send an email impersonating your domain, SPF does the blocking.

Example: Your SPF record will list Gmail's mail servers if your company (yourcompany.com) sends emails only through Gmail. Thus, if someone sent an email from your domain using some other mail server, SPF would flag it as unauthorized.

2. DKIM: Domain Keys Identified Mail

It's kind of a digital signature for your emails, which ensures that the email has not modified through transit by adding an encrypted key within the email header. The recipient's mail server checks such signatures to confirm an email as legitimate.

Example: It's like sealing up a particular envelope with a unique stamp. If seal tampering occurs, the receiver knows the email was modified or fake.

3. DMARC: Domain-based Message Authentication, Reporting, and Conformance

It is the ultimate law enforcer. It dictates the server's action once an email fails both SPF and DKIM checks-deliver, quarantine, or reject. Furthermore, DMARC writes some reports which will help you monitor unauthorized email activities.

Example: If he didn't have any valid ID (SPF and DKIM), that DMARC would decide whether to let him in flag him for further inspection, or put him on a bus back home.

Impacts of Email Authentication on Deliverability:

Lack of authentication may result in your emails

Landing in spam folders

Getting refused by the email providers

Lowering the reputation of your sender

Becoming the tool of Phishing attacks (that hurts even your brand credibility)

And with proper SPF, DKIM, and DMARC setups, you won

Higher inbox deliverability

Better sender reputation

Protection against email spoofing

Real time Example

Let's say ABC Corp produces newsletters and sends them out using a third-party service for mailing. Without SPF and DKIM, the company's mail is spammed. After they set up SPF (which listed the third-party service as an authorized sender) and DKIM (which signs their emails), mail delivery to customers started to happen regularly.

Subsequently, through DMARC activation, reports come in about any attempts of unauthorized mailing activities, and phishing email attempts using their name are blocked.

Most Important Additional Best Practices for Email Authentication

Though SPF, DKIM, and DMARC are basic and fundamental requirements, here are some extra steps that can make your email security even better:

Monitor DMARC reports with regularity: DMARC reports, of course, reveal how your emails actually get treated. Therefore, reviewing them from time to time would allow identifying and fixing authentication problems.

Update your SPF record: If there is a new email provider employed or any new service for sending emails is added, alter the SPF record appropriately.

Email marketing using a subdomain: This promotes the safety of the main domain and ensures that the company's email accounts aren't easily affected by problems with their marketing emails.

Set up BIMI: BIMI works with DMARC and attaches your brand logo next to authenticated emails improving trust factor visibility.

Create a consistent pattern of sending emails: Do not mail anything in here all of a sudden because it may create spammy effects.

Key Takeaways

The combination of SPF, DKIM, and DMARC makes spoofing and phishing harder.

Correct authentication allows better email deliverability and improves sender reputation.

In the absence of authentication, emails may just end up in the spam folder or be rejected altogether.

Keeping an active watch on DMARC reports can help you in taking proactive measures against email security threats.

Additional best practices are BIMI and subdomain usage for better protection against email threats.

Conclusion

Email authentication is a necessity for business organizations and individuals concerned with emailing. Leveraging the proper SPF, DKIM, and DMARC authentication will greatly improve email deliverability, protect the brand against phishing attacks, and ensure that messages reach the desired inboxes.

Taking the time to configure and monitor these protocols now will save one from future security breaches and ultimately lead to greater success for email marketing campaigns.

Start today-for your emails to work for you instead of against you.

Have questions or need help setting up your email authentication. Leave a comment below.