Your Emails Are Going to Spam: A Deliverability Checklist for 2026

In February 2024, Gmail and Yahoo rolled out new sender requirements that fundamentally changed email deliverability. In 2025, Microsoft followed suit. Now in 2026, the bar is even higher — and most eCommerce brands are failing to clear it.

We audit 10-15 email programs every month, and over 60% have critical deliverability issues they don't even know about. Emails silently going to spam. Engagement rates tanking. Revenue disappearing — and the brand blames "email doesn't work anymore."

Here's our complete 23-point deliverability checklist. Fix these, and you'll see open rates climb within 2-3 weeks.

Part 1: Authentication (The Non-Negotiables)

If you get nothing else right, get authentication right. Without proper authentication, inbox providers treat your emails like unverified strangers — and strangers go to spam.

1. SPF Record Configured

SPF (Sender Policy Framework) tells inbox providers which servers are allowed to send email on behalf of your domain. Without it, anyone can spoof your address. Check your DNS for a TXT record starting with "v=spf1" that includes your ESP (Klaviyo, Mailchimp, etc.).

2. DKIM Signing Active

DKIM (DomainKeys Identified Mail) adds a digital signature to every email you send, proving it hasn't been tampered with in transit. Your ESP provides the DKIM records — you add them to your DNS. Both your root domain and sending subdomain need DKIM.

3. DMARC Policy Published

DMARC tells inbox providers what to do when SPF or DKIM checks fail. At minimum, you need a monitoring policy (p=none) to collect data. Ideally, move to p=quarantine or p=reject within 3-6 months.

A proper DMARC record looks like: v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100

4. Custom Sending Domain

Stop sending from shared ESP domains. Set up a dedicated sending subdomain (e.g., mail.yourbrand.com). This gives you your own sender reputation instead of sharing one with thousands of other senders.

5. Return-Path Alignment

The Return-Path (envelope sender) should align with your From domain. Misalignment is a red flag to spam filters. Most ESPs handle this automatically when you set up a custom sending domain.

Part 2: List Hygiene

6. Remove Hard Bounces Immediately

Hard bounces (invalid addresses) should be suppressed after the first occurrence. Continuing to send to invalid addresses signals to ISPs that you don't maintain your list — a major spam indicator.

7. Sunset Unengaged Subscribers

If someone hasn't opened or clicked an email in 90-120 days, move them to a re-engagement segment. If they don't engage with the re-engagement campaign, suppress them. Keeping unengaged subscribers tanks your open rates, which tanks your sender reputation.

8. Monitor Spam Complaints

Your spam complaint rate must stay below 0.1% (that's 1 complaint per 1,000 emails). Gmail's Postmaster Tools shows your exact complaint rate. If you're above 0.1%, you need to immediately reduce send volume and clean your list.

9. Validate New Subscribers

Use double opt-in or email validation services (like ZeroBounce or NeverBounce) to verify new subscribers. Bot signups and typo'd email addresses pollute your list and hurt deliverability.

10. Scrub Spam Traps

Spam traps are email addresses specifically designed to catch spammers. They end up on your list through purchased lists, scraped addresses, or recycled abandoned addresses. Run your list through a validation service quarterly to catch them.

Part 3: Sending Practices

11. Warm Up New IPs/Domains Gradually

If you switch ESPs or set up a new sending domain, don't blast your full list on day one. Start with your most engaged 500-1,000 subscribers and gradually increase volume over 2-4 weeks. ISPs trust senders who ramp up gradually.

12. Consistent Send Volume

Sending 2,000 emails on Monday and 50,000 on Tuesday looks suspicious to ISPs. Maintain consistent daily/weekly volume. If you need to increase, do it gradually (20-30% per week maximum).

13. Segment by Engagement

Send to your most engaged subscribers first. High open and click rates in the first hour signal to ISPs that your email is wanted, which improves inbox placement for the rest of the send.

14. Respect Send Frequency Expectations

If subscribers signed up expecting weekly emails and you're sending daily, you'll see complaints spike. Set clear expectations at signup and stick to them. If you want to increase frequency, test it gradually.

15. Honor Unsubscribes Instantly

The new Gmail/Yahoo requirements mandate one-click unsubscribe via a List-Unsubscribe header. Unsubscribes must be processed within 2 days. Most ESPs handle this automatically, but verify yours does.

Part 4: Content & Design

16. Maintain a Healthy Text-to-Image Ratio

Emails that are 100% images with no text are spam filter magnets. Aim for at least 60% text, 40% images. Every image should have descriptive alt text — both for accessibility and because spam filters read alt text.

17. Avoid Spam Trigger Words

Words like "FREE!!!", "ACT NOW", "LIMITED TIME", and excessive caps/exclamation marks trigger spam filters. Write like a human, not an infomercial. Modern spam filters are sophisticated, but blatant spam language still gets flagged.

18. Use Clean HTML

Messy HTML with broken tags, excessive inline styles, or code copied from Word/Google Docs can trigger spam filters. Use your ESP's built-in editor or clean, tested HTML templates.

19. Include a Physical Address

CAN-SPAM requires a physical mailing address in every commercial email. It's not optional. Use your business address or a registered PO Box. Missing this is an instant compliance violation.

20. Test Before Sending

Use tools like Mail Tester, GlockApps, or Litmus to check your email's spam score before sending. These tools simulate how major inbox providers will evaluate your email and flag potential issues.

Part 5: Infrastructure & Monitoring

21. Set Up Google Postmaster Tools

Google Postmaster Tools is free and gives you direct insight into how Gmail sees your emails. Monitor your domain reputation, spam rate, authentication results, and delivery errors. If your domain reputation drops to "Low" or "Bad," you have a serious problem.

22. Monitor Blacklists

Check if your sending IP or domain appears on any major blacklists (Spamhaus, Barracuda, SORBS). Use MXToolbox for quick lookups. If you're blacklisted, most services have a delisting process — but it takes time, so catch issues early.

23. Track Inbox Placement (Not Just Delivery)

A 99% delivery rate doesn't mean 99% inbox placement. Emails can be "delivered" to the spam folder. Use inbox placement testing tools to see where your emails actually land across Gmail, Outlook, Yahoo, and Apple Mail.

The Quick-Fix Priority List

If you're overwhelmed, here's where to start. These five fixes will have the biggest immediate impact:

1. Fix authentication (SPF, DKIM, DMARC) — this is table stakes
2. Clean your list — remove bounces and anyone who hasn't engaged in 120+ days
3. Set up Google Postmaster Tools — you can't fix what you can't measure
4. Add one-click unsubscribe — required by Gmail/Yahoo since Feb 2024
5. Segment by engagement — send to active subscribers first

Most brands see open rates improve by 15-30% within 2-3 weeks of addressing these five items. The remaining checklist items are important for long-term health, but these five will stop the bleeding.

When to Call in Help

If your domain reputation is already "Bad" in Google Postmaster Tools, or if you're on major blacklists, self-recovery is difficult. The longer deliverability issues persist, the harder they are to fix. Sometimes a fresh sending domain with proper warmup is faster than repairing a damaged one.