Email Deliverability

What It Is

Deliverability is the infrastructure layer that determines whether outbound email reaches the inbox at all. Global inbox placement averages ~84% (Validity 2025) — roughly 1 in 6 legitimate emails doesn't land. For warmed, authenticated B2B cold email, median Google Workspace placement is ~87% (Hunter 31M-email dataset).

Domain Hierarchy

  • Primary domain (acme.com) — warm/internal/curated outreach only; never cold mass outreach.
  • Warm domains (go.acme.com) — dedicated, authenticated, warmed, monitored; used for sequences.
  • Throwaway domains — high-volume testing; rotated frequently; higher reputation risk.

Rule of thumb: 1 domain per 50–100 emails/day; use a custom tracking domain separate from the sending domain.

The Three Authentication Layers

  • SPF — authorizes which servers may send for your domain
  • DKIM — cryptographic signature proving the email wasn't altered
  • DMARC — tells receivers what to do with SPF/DKIM failures (p=quarantine minimum, p=reject preferred)

Warm-Up Ramp (3–4 weeks minimum)

Week Daily limit per domain
1 5–10
2 20–30
3 50–75
4+ 75–150

Never jump from 10 to 500/day. Red flags: bounce rate >5% (reputation damage), complaint rate >0.1% (blacklist risk), spam-trap hits (immediate blacklisting), sudden volume spikes.

How It Applies to Marketing Factory

Deliverability is the hard gate before any outbound agent scales: domains must be authenticated and warmed, and bounce/complaint rates monitored continuously, with an automatic throttle/pause when red-flag thresholds trip. Treat list verification (ZeroBounce/NeverBounce) as a mandatory pre-send step — garbage lists destroy domain reputation faster than any copy can recover.

Referenced from: outbound-playbook