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10/10 Email Deliverability Guide

Most outbound tools skip this entirely. Their users end up in spam and wonder why nobody responds.

We scored 10/10 on mail-tester.com in production. This is the exact setup.

Step 1: Buy a Secondary Domain (~$12/year)

Never send cold outreach from your primary company domain.

If your company is acme.com, buy a secondary outreach domain:

  • tryacme.com
  • acmehq.com
  • getacme.com
  • acmeteam.com

Where to buy: Namecheap, Cloudflare Registrar, Google Domains (~$12/year).

Your primary domain stays clean. If the outreach domain ever gets flagged, you replace it for $12. Rebuilding a burned primary domain takes months.

Step 2: Set Up Email on the Secondary Domain

Google Workspace ($7/month): workspace.google.com

Microsoft 365 ($6/month): microsoft.com/microsoft-365

Create your sending address: you@yoursecondary-domain.com

For Gmail app passwords (required for SMTP): Google Account → Security → 2-Step Verification → App passwords Name it "Sniper" — save the 16-character key for config.yaml.

Step 3: Configure DNS Authentication

This is the most important step. All three records go in your domain registrar's DNS settings.

SPF Record

Tells receiving servers that Google (or Microsoft) is authorized to send from your domain.

Type:  TXT
Host:  @
Value: v=spf1 include:_spf.google.com ~all

For Microsoft 365:

Value: v=spf1 include:spf.protection.outlook.com ~all

DKIM Record

Cryptographically signs your emails. Receiving servers verify the signature to confirm authenticity.

Google Workspace:

  1. Admin Console → Apps → Google Workspace → Gmail → Authenticate Email
  2. Click "Generate New Record" — select 2048-bit key
  3. Copy the TXT record value to your DNS
  4. Return to Admin Console → click "Start Authentication"

Microsoft 365:

  1. Microsoft 365 Admin Center → Settings → Domains → your domain
  2. Follow the DKIM setup wizard — it generates the DNS records for you

DMARC Record

Tells receiving servers what to do if SPF or DKIM fails. Start with p=none (monitor only) — don't use p=reject until you've confirmed everything is working.

Type:  TXT
Host:  _dmarc
Value: v=DMARC1; p=none; rua=mailto:you@yoursecondary-domain.com

DNS propagation takes up to 48 hours. Wait before testing.

Step 4: Warm Up the Domain (2 Weeks)

A brand-new domain with zero sending history looks suspicious. Warm it up before running the Sniper at volume.

Week Daily sends Who to send to
Week 1 5–10/day Real contacts: colleagues, friends, any known address
Week 2 15–25/day Expand to more contacts, mix in a few cold sends
Week 3+ Ready for Sniper at 25–50/day

Rules during warmup:

  • Send real emails, not test messages. Real replies are the strongest warmup signal.
  • Don't use a warmup service — they use fake addresses that receiving servers recognize.
  • If someone replies, reply back. Engagement signals are everything.

Step 5: Verify Your Score

Before running the Sniper at any volume, check your score at mail-tester.com.

  1. Go to mail-tester.com
  2. Copy the test email address they give you
  3. Send a plain-text email from your outreach address to that address
  4. Return to mail-tester.com and click "Then check your score"

Target: 9/10 or above before sending cold outreach.

If you score below 9:

  • Check which DNS records are missing (mail-tester shows you exactly what failed)
  • Verify SPF, DKIM, DMARC are all active
  • Make sure you're sending plain text, not HTML-heavy templates

Why This Matters

Cold email is a deliverability game before it's a copy game. The best subject line in the world lands in spam if your domain isn't authenticated.

Our production stats with this setup in place:

  • 10/10 on mail-tester.com
  • 52.9% open rate on cold B2B email
  • <1% bounce rate (Hunter verification at 90%+ confidence)

Most cold outreach tools average 15–20% open rates. The difference isn't the copy — it's the infrastructure.

SMTP Settings Reference

Gmail / Google Workspace

email:
  smtp_host: smtp.gmail.com
  smtp_port: 587
  email: you@yoursecondary-domain.com
  app_password: YOUR_16_CHAR_APP_PASSWORD

Microsoft 365 / Outlook

email:
  smtp_host: smtp.office365.com
  smtp_port: 587
  email: you@yoursecondary-domain.com
  app_password: YOUR_APP_PASSWORD

Other SMTP (any provider)

email:
  smtp_host: mail.yourprovider.com
  smtp_port: 587
  email: you@yoursecondary-domain.com
  app_password: YOUR_PASSWORD

Scaling Past 50/day

SMTP from a single inbox tops out around 50–75 high-quality emails/day before you risk deliverability issues.

When you need more:

  • Smartlead or Instantly — multi-inbox rotation, built-in warmup, analytics
  • Set method: smartlead or method: instantly in config.yaml
  • These platforms handle inbox rotation automatically across multiple sending accounts

Don't try to push a single inbox to 200/day. Split across 4 inboxes at 50/day instead.