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Beginner Deliverability Guide 5 min read Updated September 2026

Why Your Cold Emails Go to Spam (And How to Fix It in Plain English)

You spent hours writing the perfect pitch. You hit send. And... silence. No replies, no opens. That's because your email never reached their inbox. Here is the no-BS explanation of what went wrong and how to fix it in 15 minutes.

The 30-Second Summary
  • Set Your 3 Passports: SPF, DKIM, and DMARC prove you aren't a scammer impersonating someone else.
  • Never Bounce > 2%: Sending to dead email addresses destroys your sender reputation instantly.
  • Warm Up Your Mailbox: Like stretching before running, new inboxes need a slow ramp-up before sending bulk volume.

1. The Real Reason You're in Spam

Imagine a mail carrier delivering physical envelopes to an office building. If a stranger wearing a ski mask drops off 500 unmarked letters claiming to be from the CEO, the building security will throw them straight into the incinerator.

Google (Gmail) and Microsoft (Outlook) are that building security. They don't hate your cold email. They just don't know who you are yet. If your domain looks suspicious or unverified, their automatic spam filters hide your email so the recipient never even sees it.

Crucial Rule: Spam filters do not read your email like a human does. They judge you on three simple technical tests before anyone ever reads your subject line.

2. The 3 Security Passports (SPF, DKIM, DMARC)

To convince Gmail and Outlook that you are a legitimate human and not an offshore scammer, your domain needs three free DNS records. Think of them as your company's digital passport.

1SPF (Sender Policy Framework)

The Guest List

In Plain English: A public list in your domain settings that says: "These specific servers (like Google Workspace or Outlook) are allowed to send mail on my behalf." If an email comes from a server not on this list, it looks like a fake.

2DKIM (DomainKeys Identified Mail)

The Wax Seal

In Plain English: In the old days, kings stamped hot wax on letters with their private signet ring. DKIM is a digital signature attached to every email. It proves nobody tampered with or altered your message while it traveled across the internet.

3DMARC (Domain-based Message Authentication)

The Security Guard

In Plain English: DMARC tells the receiving mail server what to do if someone fails your SPF or DKIM test. It tells Gmail: "If someone sends an email pretending to be me but lacks my signature, reject it immediately!"

Want to see if your domain passes SPF, DKIM, and DMARC?Free 10-Sec Test →

3. The 2% Bounce Trap

What happens when you send an email to an address that no longer exists (e.g. someone left their company)? The email "bounces" back as undeliverable.

Here is what Google and Outlook think when your emails bounce:

"Legitimate humans know who they are emailing. Only spammers buy shady lists and blast thousands of dead addresses. Flag this sender as spam immediately."

The Golden Rule: If your bounce rate climbs above 2% (more than 2 bounces out of every 100 emails sent), your domain reputation drops off a cliff.

💡 The Easy Fix: Always run your prospect list through an email verifier like Shakehand's real-time bounce checker before launching a campaign. It tests the email server live without sending an email!

4. Sneaky Words Spam Filters Hate

Spam filters use AI natural language models to read your copy. If you sound like an infomercial, you are going to the spam bin.

Don't Say This (Spam Triggers)
  • ❌ "100% Guaranteed"
  • ❌ "Free consultation / Free gift"
  • ❌ "Act NOW / Limited time offer"
  • ❌ "Earn $$$ / Fast cash"
  • ❌ Multiple exclamation marks (!!!) & ALL CAPS
Say This Instead (Natural & Human)
  • ✅ "Quick question regarding [Company]"
  • ✅ "Are you currently exploring ways to..."
  • ✅ "Open to seeing a 2-minute overview?"
  • ✅ "Thought this might be relevant for your team"
  • ✅ Short, conversational, 1-2 sentence paragraphs

5. Sending Too Fast, Too Soon

If you buy a brand new domain today (e.g. getyourcompany.com) and immediately blast 300 emails tomorrow, Google will blacklist you by noon.

Why? Because brand new mailboxes have zero history. You must "warm up" your mailbox over 2 to 3 weeks:

Safe Sending Schedule:
Week 1: 5 to 10 emails per day with automated warmup
Week 2: 15 to 25 emails per day
Week 3+: 30 to 40 emails per day per mailbox (never more than 50!)

Want to send 500 emails a day? Don't send them from one mailbox! Use 10 connected mailboxes sending 50 each. Shakehand handles this automatically with multi-inbox rotation.

6. Your 15-Minute Action Checklist

Follow these 5 steps to permanently get your cold emails into the primary inbox:

1
Run a free DNS check
Verify that SPF, DKIM, and DMARC are all showing green passes on your domain.
2
Clean your email list
Remove all unverified, catch-all, and high-risk emails to keep your bounce rate under 2%.
3
Turn on Automated Warmup
Let your mailbox exchange friendly emails and generate replies in the background.
4
Strip out image attachments & tracking pixels
Heavy HTML templates and tracking links trigger spam filters. Plain text wins every time.
5
Keep daily volume under 50 per inbox
Distribute your volume across multiple sender addresses to stay under radar.

7. Plain-English FAQ

Can I send cold emails from my primary company domain?

Never! Always buy a secondary domain (like trycompany.com or companyhq.com). If your secondary domain ever gets flagged, your main company email (invoices, team emails) remains 100% safe.

How long does it take to fix a domain that went to spam?

Usually 14 to 21 days of continuous warmup with zero cold outreach will restore your domain reputation score back above 85%.

Does Shakehand do this automatically?

Yes! Shakehand validates your SPF/DKIM/DMARC, checks emails for bounces before firing, and rotates warm mailboxes automatically so you never have to worry about spam filters.

100% Automated Deliverability

Ready to Land in the Primary Inbox Every Single Time?

Shakehand verifies prospect emails, audits your domain health, and rotates warm inboxes automatically. Start sending for free today.