SPF, DKIM, DMARC: Why Your Emails Land in Spam

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If you’ve ever sent a cold email campaign or a newsletter only to find your open rates mysteriously plummet, you’ve probably been hit by the silent gatekeepers of modern email delivery: SPF, DKIM, and DMARC.

They sound technical (and honestly, they are), but every marketer, founder, and growth operator needs to understand them. Because today, great copy isn’t enough — your emails have to prove they’re trustworthy before they ever reach an inbox.

Let’s break down what these acronyms mean, why they matter, and how to fix your deliverability before your next send.

Why Emails Land in Spam (Even When You’re Legit)

Email providers like Gmail, Outlook, and Yahoo receive billions of messages daily. To protect users from phishing and spoofing, they use multiple layers of filters to verify who is sending a message and whether that sender is real.

If your authentication setup is incomplete, those providers get suspicious — and your carefully crafted email ends up buried in the Promotions tab or, worse, spam.

That’s where SPF, DKIM, and DMARC come in.

SPF: The Bouncer at the Door

SPF (Sender Policy Framework) tells receiving servers which mail servers are allowed to send emails on behalf of your domain.

Think of it like a guest list. If your email comes from a server not on that list, it’s denied entry.

For example, if your company domain is brandtribe.com, and you use both Gmail and an email tool like Instantly or Mailchimp, your SPF record should list both.

What it looks like:
v=spf1 include:_spf.google.com include:mailgun.org ~all

Without a valid SPF record, your emails are like party crashers — they might sneak in once or twice, but sooner or later, they’re bounced out.

DKIM: The Signature That Proves You’re You

DKIM (DomainKeys Identified Mail) adds a digital signature to your outgoing emails.

When your message hits the recipient’s inbox, the receiving server checks that signature against your domain’s public key (stored in your DNS). If it matches, the server knows the message hasn’t been tampered with and actually came from you.

It’s like sealing an envelope with a wax stamp — proof that it’s authentic.

Why it matters:
Without DKIM, your emails could be modified mid-transit (or simply flagged as unsafe), and ISPs will downgrade your reputation.

DMARC: The Policy That Enforces the Rules

DMARC (Domain-based Message Authentication, Reporting & Conformance) ties SPF and DKIM together and tells receiving servers what to do if a message fails those checks.

A DMARC policy can be:

• None – just monitor and report.

• Quarantine – send suspicious emails to spam.

• Reject – block them outright.

Example record:
v=DMARC1; p=quarantine; rua=mailto:[email protected]

DMARC also gives you visibility. You get reports showing who’s sending emails on your behalf — sometimes revealing unauthorized tools or spoofing attempts you didn’t know existed.

How to Set Them Up

1. Access your domain’s DNS settings.
   Most are managed in GoDaddy, Namecheap, or your hosting provider.

2. Add or update the TXT records for SPF, DKIM, and DMARC.
   Your email service (Google Workspace, Zoho, Mailgun, etc.) will provide exact entries.

3. Validate using tools like:

   • MXToolbox

   • Dmarcian

   • Google Admin Toolbox

4. Wait for propagation. It can take a few hours to 48 hours for DNS changes to apply.

Best Practices for Better Deliverability

Even after authentication, spam filters still monitor engagement and content quality. Follow these to stay in the safe zone:

• Warm up new domains gradually. Don’t blast hundreds of cold emails from a fresh address.

• Avoid spammy language (“Free!”, “Guaranteed!”, “Act now!”) and too many links or images.

• Keep sending volume consistent to avoid reputation spikes.

• Use a custom tracking domain if you’re using outreach tools — generic tracking links raise flags.

• Monitor your domain reputation via tools like Postmaster Tools (Gmail) or Mail-Tester.

The Human Side of Deliverability

Here’s the paradox: the more email security improves, the more trust becomes the differentiator. Authentication protocols aren’t just technical hoops — they’re part of building credibility with your audience.

When subscribers see your brand in their inbox, they’re more likely to open, click, and engage if your emails consistently land where they should.

Deliverability isn’t just about DNS records. It’s about sending useful, human, expected messages — and making sure the infrastructure behind them reflects that professionalism.

The GTM Guild Takeaway

In modern GTM strategy, technical hygiene equals growth hygiene. You can’t scale cold outreach, newsletters, or lifecycle campaigns without a solid sender reputation.

SPF, DKIM, and DMARC are the invisible foundation that ensures your marketing efforts actually reach humans, not spam folders.

So before you tweak your next subject line or design a new template, check your DNS. Because even the best email can’t convert if it’s never seen.

More articles on Cold emailing;

Until next time,

—Team GTM Guild