When it comes to cold email, nothing kills momentum faster than watching your perfectly crafted messages disappear into the spam folder. You think it’s your copy, or maybe your list… but the truth is, spam placement almost always comes down to infrastructure and habits.

Here’s the reality: spam filters don’t just look at your subject line. They track how you send, where you send from, and how people engage with your emails. If something looks off, you’re flagged.

This post breaks down the 10 most common reasons cold emails get trapped in spam—and exactly how to fix them.

1. No SPF/DKIM/DMARC = No Trust

👉 Fix it: Add all three records to every sending domain. Tools like Mission Inbox can check your DNS setup automatically so you know you’re not flying blind.

2. Brand-New Domains Sending Like Veterans

👉 Fix it: Warm up gradually. Start with a trickle, build slowly, and use warmup systems that simulate real human engagement.

Start your domain warm-up today →

3. Dirty Lists

👉 Fix it: Clean your lists regularly. Never buy data dumps. Keep only verified, engaged addresses

4. Burned Reputation (IP or Domain)

👉 Fix it: Rotate domains and mailboxes. Think of it as spreading risk instead of putting all your eggs in one basket.

Try Mission Inbox’s domain rotation system

5. Blacklisted Domains

👉 Fix it: Monitor blacklist status daily. If you get flagged, either delist or swap in a clean domain from your rotation.

6. Burned Reputation (IP or Domain)

👉 Fix it: Rotate domains and mailboxes. Think of it as spreading risk instead of putting all your eggs in one basket.

7. Inconsistent Sending Patterns

👉 Fix it: Keep sending steady. Don’t disappear for weeks and then blast thousands. Build a consistent rhythm that mailbox providers trust.

8. Free Email Accounts

👉 Fix it: Always use a custom domain tied to your company. This is deliverability 101. Set up your first custom sending mailbox

9. Over-Sending From One Mailbox

👉 Fix it: Spread your campaigns across multiple mailboxes and domains. This keeps volume natural and avoids reputation burnouts.

10. Weak Engagement

👉 Fix it: Segment, personalize, and target better. Don’t chase volume—chase relevance. Better engagement = better inbox placement.

Final Takeaways

If your cold emails keep going to spam, it’s usually not about clever copy—it’s about how you’re sending. Authentication, list hygiene, pacing, and monitoring are the foundation. Get those right, and your copy has a fighting chance.

At Mission Inbox, we built our platform to catch these issues before they tank your campaigns. From DNS checks to blacklist monitoring to automated warmup, our goal is simple: keep your cold emails out of spam, and in front of prospects.

Stop guessing about spam placement. Run a deliverability test with Mission Inbox today →