The 3 Pillars of Email Deliverability: Relevance, Trust, and Engagement

When I talk to business owners about getting out of the spam folder and landing in the inbox, the conversation usually starts in the same place:

“Isn’t deliverability just about making sure my SPF, DKIM, and DMARC are set up and my email platform handles the rest?”

Yes… and no.

Don't get me wrong, the tech matters, as without proper email authentication, you’re not even allowed in the Mailbox anymore. But what really determines whether you make it into your customer’s inbox and not the spam folder isn’t just about passing the technical checks.

Google, Yahoo, Microsoft, and other mailbox providers have evolved their filtering systems to think much more like people. They’re not just scanning for spammy links and malformed HTML or specific keywords. They’re asking:

• Is this email relevant to the person receiving it?
• Does it come from a sender we can trust?
• Do people actually engage with it?

These three questions form the pillars of modern spam filtering and deliverability: Relevance, Trust, and Engagement.

And if you want your emails consistently reaching the inbox and not the spam folder or even worse, blocked, you need to build strength in all three.

Why These Three Pillars Matter Now More Than Ever

A decade ago, email filtering was largely “top-down”, your sender reputation score determined most of your inbox placement. If your IP was clean, your domain had a good history, and you weren’t tripping known spam words, you were fine.

That’s not how it works anymore.
Today, mailbox providers use AI-driven, behavior-based filtering. Instead of just asking “Is this sender clean?” they ask “Do recipients like this sender’s content?”

That means your content quality and audience behavior are now just as important as your domain reputation. The filter decisions are made for each individual user and each individual message, which is why two people on the same list might see different results.

It’s no longer enough to be “safe.” You have to be wanted.

Pillar 1: Relevance: The Inbox Is a Competitive Arena

Every day, you’re bombarded with promotions, newsletters, updates, and random cold pitches. The average email user is receiving 121 emails PER DAY on average. Think of your own inbox, which ones emails you actually open? Why do you open the emails that you do?

You open the ones that feel meant for you. That’s relevance.

What Relevance Looks Like

Relevance means:

• The content matches the subscriber’s interests, preferences, and stage in the buying journey.
• The timing of the send makes sense — you’re not sending a “Holiday Sale” email in mid-January.
• The offer or message connects to something the subscriber has done recently (clicked, browsed, purchased).

Example:
If someone downloads your guide on “10 Ways to Grow Your Garden Organically,” the next few emails should be about organic gardening tips, products, and resources, not about pet grooming or holiday recipes.

How Mailbox Providers Measure Relevance

They don’t “read” your content the way a person does, but they measure how recipients react:

• Do people open?
• Do they click?
• Do they scroll through the email (in clients that measure read time)?
• Do they delete without opening?
• Do they never open the email at all?

Low engagement signals poor relevance, and poor relevance pushes future emails toward spam or Promotions.

How to Improve Relevance

1. Segment your list tightly. Don’t send every email to every subscriber.
2. Use behavior-based triggers. Follow up on clicks, visits, and downloads with related content.
3. Write for a single audience at a time. The more specific the message, the more it will resonate.
4. Test send timing. Your audience might be more responsive at 8 AM on Tuesdays than 3 PM on Fridays.

Pillar 2: Trust: The Foundation of Inbox Placement

Without trust, your email never gets a fair shot at relevance or engagement  because it may not even be delivered.

Trust comes from both technical trust (email authentication) and brand consistency.

Technical Trust

This is where authentication protocols (SPF, DKIM, DMARC) come in. They prove to mailbox providers that:

• You are who you say you are.
• Your messages haven’t been tampered with in transit.
• You’re following modern sending standards.

Failing these checks can land you in spam or blocked before your content is even considered.

Brand Trust

Even with perfect authentication, you can still lose trust if:

• Your domain is new and has no sending history.
• Your sending patterns are erratic or suspicious.
• Your emails look and feel different from what people expect from your brand.

Subscribers are quick to distrust anything that feels off. If your “From” name changes often, your emails suddenly start linking to odd domains, or your design is inconsistent, both people and filters take notice.

How Mailbox Providers Measure Trust

They look at:

• Your domain and IP’s historical complaint rate.
• Whether you send to spam traps or invalid addresses.
• The consistency of your sending volume and frequency.
• The number of positive vs. negative engagement signals (opens, clicks vs. spam reports, unsubscribes).

How to Build Trust

1. Authenticate fully. Align SPF, DKIM, and DMARC across all sending sources.
2. Warm up new domains. Don’t start blasting large volumes from a fresh domain.
3. Keep branding consistent. Your emails should match your website, social media, and prior sends.
4. Send to people who opted in. Avoid purchased or scraped lists at all costs.

Pillar 3: Engagement: The Currency of Deliverability

If relevance is the message and trust is the foundation, engagement is the scorecard.

Engagement tells mailbox providers how much your audience values your emails. High engagement says “people want this,” which keeps you in the inbox. Low engagement says “people ignore this,” which nudges you toward promotions or spam.

Positive Engagement Signals

• Opening your emails regularly
• Clicking on links
• Replying to messages
• Moving emails from Promotions to Primary
• Marking “Not Spam”
• Adding you as a contact

Negative Engagement Signals

• Deleting without opening
• Ignoring multiple sends
• Marking as spam
• Unsubscribing immediately after opening

How to Drive Engagement

1. Make the first line count. Your subject line and preview text must earn the open.
2. Get to the point fast. Respect their time: clarity beats cleverness.
3. Make it skimmable. Use short paragraphs, bullet points, and bold for key ideas.
4. Include clear, benefit-driven CTAs. Every email should have a reason to click.
5. Re-engage before it’s too late. Target subscribers who haven’t engaged in 30–60 days with a win-back campaign.

Why You Can’t Ignore Any of the Three Pillars

Here’s the catch: you can’t just focus on one pillar and ignore the others.

• Great relevance with poor trust still gets you filtered.
• Strong trust but no engagement eventually erodes your inbox placement.
• High engagement today can disappear if you lose relevance tomorrow.

These pillars are interconnected, a weakness in one undermines the others.

The S.M.A.R.T. Connection

At EmailSmart, we’ve built the S.M.A.R.T. framework to tackle deliverability holistically:

• S – Start Smart & Shift Your Thinking (mindset shift toward engagement-driven sending)
• M – Manage Your Engagement (list hygiene, segmentation, and activity monitoring)
• A – Authenticate Your Emails (SPF, DKIM, DMARC alignment)
• R – Reputation is Everything (protecting your sender reputation)
• T – Transform Your Content (making it relevant, trustworthy, and engaging)

Relevance, Trust, and Engagement aren’t random ideas, they’re baked into the M, R, and T in this framework.

Real-World Example: How Fixing the Pillars Changed the Game

We worked with a mid-sized e-commerce brand whose emails had slowly slipped into Gmail’s Promotions and spam tabs. Their open rates dropped from 24% to 9% in six months.

The problems:

• They were sending every email to the entire list (low relevance).
• They had SPF/DKIM alignment, but DMARC was missing (trust gap).
• 60% of the list hadn’t clicked anything in over 90 days (low engagement).

The fixes:

• Segmented by behavior and purchase history to send targeted offers.
• Implemented DMARC.
• Paused sending to long-term inactives, ran a win-back campaign.

The only thing that changed was how we applied relevance, trust, and engagement.

Final Thoughts

If your emails aren’t getting seen, it’s rarely just a technical problem. More often, it’s because you’ve let one or more of these three pillars weaken.

• Relevance keeps people interested.
• Trust gets you through the gate.
• Engagement keeps you there.

Ignore them, and you’ll fade into the background noise of the inbox. Strengthen them, and your email marketing becomes one of the highest-ROI channels in your business.

Want to know how you score on the 3 Pillars?
We’ll run a performance check on your domain, look at your audience engagement patterns, and give you a clear action plan to strengthen your deliverability.

[Schedule Your Performance Check ]

Frequently Asked Questions About Email Deliverability

1. What is email deliverability and why is it important?

Email deliverability is the ability of your emails to successfully reach the inbox instead of the spam folder. It’s important because poor deliverability means fewer people see your emails, lowering open rates, click rates, and revenue.

2. How can I stop my emails from going to spam?

To avoid spam filters, focus on three core areas: sending relevant content, building trust with proper authentication (SPF, DKIM, DMARC), and driving positive engagement from your audience.

3. What factors affect whether my emails land in the inbox?

Mailbox providers like Gmail and Outlook look at your sender reputation, the relevance of your content, trust signals (authentication and safe links), and engagement metrics like opens, clicks, and spam complaints.

4. How do Gmail and Outlook decide if my emails are spam?

They use AI-driven filters that analyze your sending reputation, content quality, and how recipients interact with your emails. Low engagement or trust signals can send your emails to spam, even if your list is legitimate.

5. How can I make my marketing emails more relevant to my audience?

Segment your list, personalize your subject lines, and send content that matches each subscriber’s interests, past actions, and stage in the buying journey.

6. Does email relevance affect spam filtering?

Yes. If your emails are consistently ignored, deleted, or marked as spam, mailbox providers assume they’re irrelevant and will filter them out of the inbox.

7. How do I build trust with mailbox providers like Gmail and Outlook?

Authenticate your emails (SPF, DKIM, DMARC), send from a consistent domain, maintain a good sending history, and avoid sudden spikes in sending volume.

8. What is domain reputation and how do I improve it?

Domain reputation is a trust score mailbox providers assign to your sending domain. You can improve it by sending to engaged subscribers, avoiding spam traps, and keeping your bounce and complaint rates low.

9. Why does my email go to spam even though authentication passes?

Passing SPF, DKIM, and DMARC proves your identity, but filters also judge your content quality and engagement. Poor relevance or low engagement can still land you in spam.

10. How do I keep my sending domain from being flagged as suspicious?

Maintain consistent sending patterns, avoid spammy links, send only to people who opted in, and keep your list clean by removing inactive or invalid addresses.

11. What is email engagement and why does it matter?

Email engagement is how recipients interact with your emails — opening, clicking, replying, or moving them to the primary inbox. High engagement boosts deliverability; low engagement can harm it.

12. How do I increase email open and click rates?

Use benefit-driven subject lines, relevant offers, clear CTAs, and send at the times your audience is most active. Regularly test and refine your approach.

13. What engagement metrics do mailbox providers track?

They track opens, clicks, replies, spam reports, unsubscribes, deletes without opening, and moves between folders (such as Promotions to Primary).

14. How do I re-engage inactive subscribers?

Run a win-back campaign with targeted offers or valuable content. If they remain inactive, remove them from regular sends to protect your sender reputation.

15. How do spam filters use engagement data to decide inbox placement?

Positive engagement (opens, clicks, replies) signals that people want your emails, which improves inbox placement. Negative engagement (ignores, deletes, spam reports) pushes your emails toward spam.

16. Why do my open rates keep dropping?

Declining open rates may indicate your emails are losing relevance, landing in spam or Promotions, or that your audience’s preferences have shifted.

17. How do I run an email deliverability performance check?

Use deliverability tools or work with an expert to analyze your authentication setup, sending reputation, engagement metrics, and content quality.

18. What is the best way to warm up a new domain?

Start by sending small volumes to your most engaged contacts, then gradually increase volume over several weeks while monitoring engagement and reputation.

19. How do I know if my engagement rate is hurting my deliverability?

If your open or click rates are consistently below industry benchmarks and your inbox placement is dropping, low engagement may be the cause.

20. What are the top ways to improve email inbox placement?

Focus on sending relevant content, authenticating your domain, maintaining a clean list, and driving engagement through targeted campaigns.