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Email Deliverability: Why Your Emails Land in Spam

If your emails aren't reaching the inbox, nothing else matters. Here's why emails go to spam and how to fix it.

deliverability spam email infrastructure technical

You can write the perfect email with the perfect subject line and the perfect CTA. None of it matters if your email lands in spam.

Deliverability is the unsexy foundation that everything else depends on.

Why Emails Go to Spam

1. Poor Sender Reputation

Email providers track your sending behavior. If too many people mark your emails as spam, ignore them, or if you send to invalid addresses, your reputation tanks.

Think of it like a credit score for your email domain.

2. Missing Authentication

Three things you need set up:

  • SPF — tells servers which IPs can send on your behalf
  • DKIM — adds a digital signature to verify your emails
  • DMARC — tells receiving servers what to do with unauthenticated emails

If you don’t have all three, you’re basically sending emails without an ID.

3. Bad List Hygiene

Sending to:

  • Purchased email lists (never do this)
  • Old, stale addresses
  • Spam traps (fake addresses set up to catch spammers)
  • People who didn’t opt in

All of these destroy your deliverability.

4. Spammy Content

Things that trigger spam filters:

  • ALL CAPS in subject lines
  • Excessive exclamation marks!!!
  • Spam trigger words (“free,” “act now,” “limited time”)
  • Too many images, not enough text
  • Misleading subject lines
  • No unsubscribe link

5. Inconsistent Sending

Going from 0 emails to 50,000 in one day looks suspicious. Email providers want to see consistent, gradual sending patterns.

How to Fix It

Clean Your List Regularly

  • Remove hard bounces immediately
  • Re-engage or remove subscribers who haven’t opened in 90 days
  • Use double opt-in for new subscribers
  • Never buy or rent email lists

Authenticate Your Domain

Set up SPF, DKIM, and DMARC. Your email service provider should have guides for this. It takes 30 minutes and lasts forever.

Warm Up New Domains

If you’re sending from a new domain:

  1. Start with 50-100 emails/day to your most engaged subscribers
  2. Gradually increase volume over 2-4 weeks
  3. Monitor bounce rates and spam complaints
  4. Only scale when metrics are healthy

Monitor Your Metrics

Watch these numbers:

  • Bounce rate — keep under 2%
  • Spam complaint rate — keep under 0.1%
  • Open rate — if it drops suddenly, you have a problem
  • Unsubscribe rate — healthy is under 0.5% per email

Make Unsubscribing Easy

Counterintuitive, but true: making it easy to unsubscribe improves your deliverability. A clear unsubscribe link means people leave your list instead of hitting “report spam.”

The Bottom Line

Deliverability isn’t set-it-and-forget-it. It requires ongoing maintenance. But get it right, and every other metric improves automatically.