Cold Email Deliverability: The Technical Checklist Most Agencies Ignore

You wrote the perfect cold email. Personalized subject line, compelling hook, clear CTA. You hit send on 500 prospects.

Three replies.

It's not your copy. It's your deliverability. Your emails are landing in spam, promotions, or getting silently dropped — and you'd never know.

Why deliverability matters more than copywriting

The best cold email in the world is worthless if it never reaches the inbox. And most outbound setups are broken from day one because the technical foundation was skipped.

Here's the checklist.

DNS records: the non-negotiable foundation

Before you send a single email, your sending domain needs three DNS records configured correctly:

• SPF (Sender Policy Framework) — tells mail servers which IPs are authorized to send on your behalf
• DKIM (DomainKeys Identified Mail) — cryptographic signature proving the email wasn't tampered with
• DMARC (Domain-based Message Authentication) — policy that tells receiving servers what to do with unauthenticated mail

If any of these are missing or misconfigured, your emails are flagged immediately.

Pro tip: Never send cold outreach from your primary domain. Use a dedicated sending domain (e.g., mail.yourdomain.com or getleads-yourbrand.com) so your main domain reputation stays clean.

Email warm-up: you can't skip this

A brand-new email address has zero reputation. If you start blasting 100 emails/day from it, you'll get blacklisted within a week.

Warm-up means gradually increasing sending volume while maintaining positive engagement signals (opens, replies, not-spam). Most tools automate this:

• Week 1: 5–10 emails/day
• Week 2: 15–25 emails/day
• Week 3: 30–50 emails/day
• Week 4+: Scale to your target volume

Keep warm-up running even after you start campaigns. It's not a one-time step.

Sending limits and rotation

Even after warm-up, you shouldn't send 200+ emails from a single mailbox. Best practice:

• Max 50 cold emails per mailbox per day
• Rotate across 3–5 mailboxes to spread volume
• Stagger sends throughout the day (no 500-email bursts at 9am)
• Track bounce rates — if you exceed 3%, pause and clean your list

List hygiene

Bad data kills deliverability. Before any campaign:

• Verify every email address (use a verification API, not "trust the source")
• Remove catch-all domains or risky addresses
• Never send to role-based addresses (info@, support@, team@)
• Remove anyone who bounced, unsubscribed, or marked you as spam

Monitoring what matters

Track these metrics per campaign:

• Deliverability rate — % of emails that didn't bounce (target: >97%)
• Open rate — % opened (target: >50% for cold)
• Reply rate — % that replied (target: >5%)
• Spam complaint rate — must stay below 0.1%
• Bounce rate — must stay below 3%

If your open rate is below 30%, it's almost certainly a deliverability problem, not a copywriting problem.

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We configure all of this as part of every lead system build. Book a call to see what your setup looks like.