The 2026 Cold Email Deliverability Checklist

Register a dedicated sending domain — never your primary business domain

If the sending domain gets flagged, your main domain (website, employee email, transactional mail) stays clean. Patterns like getacme.com, tryacme.com, or acmehq.com work well.

Use a .com TLD only

.com domains have the highest baseline trust with inbox providers. .co, .io, or .net TLDs face higher scrutiny in spam filters.

Add SPF record: v=spf1 include:[your-ESP] ~all

SPF tells receiving servers which mail servers are authorized to send on your behalf. Keep DNS lookups under 10. Use ~all (soft fail) during warmup, then switch to -all (hard fail) once established.

Configure DKIM with a 2048-bit key (minimum)

Generate the key pair through your email sending platform. Add the public key as a TXT record at [selector]._domainkey on your domain. Rotate keys every 6–12 months.

Set DMARC to monitoring mode first: p=none; rua=mailto:dmarc@yourdomain.com

Start in p=none for weeks 1–4 to collect reports without affecting delivery. Move to p=quarantine (25%) at week 5, then p=reject at week 9+ for Scale plan domains.

Verify all three records with MXToolbox before sending

Go to mxtoolbox.com → Email Health check. Confirm SPF, DKIM, and DMARC all resolve correctly. DNS propagation can take 24–48 hours after setup.

Wait at least 14 days after registering a new domain before sending cold email

Day 0: Purchase domain and configure DNS records. Days 1–3: Send personal, non-cold emails (newsletters signups, emails to colleagues). Days 7–14: Run warmup tool. Day 14+: Begin cold outreach at warmup volumes.

Set up mailboxes with a real person's name (e.g., sarah@getacme.com)

Never use "From: Acme Inc" — this looks like marketing. The "From" name should be a real person. Keep 1–2 mailboxes per domain for Starter, 2–3 for Growth, 3–5 for Scale.

Register domain with Google Postmaster Tools

Google Postmaster Tools is the most authoritative source for Gmail deliverability. It shows your domain reputation (High, Medium, Low, Bad) and spam rate as reported by Gmail users.

Send a mix of personal emails in the first 7 days to build engagement history

Sign up for newsletters, email teammates, forward interesting articles. The goal is to create a normal-looking email history before the warmup tool takes over.

Use an automated warmup service (Instantly, Lemwarm, Warmbox, or Mailreach)

These tools send and receive emails between a network of real inboxes, simulating genuine engagement. Enable 'reply' and 'mark as important' actions for maximum signal.

Phase 1 (Days 1–7): Start at 5 emails/day, reach 10 by day 7

Only send to known, engaged contacts. Aim for at least 50% Gmail/Google Workspace recipients. Ensure open rates stay above 40%.

Phase 2 (Days 8–14): Increase to 30 emails/day, introduce cold prospects (max 50% of volume)

Run inbox placement tests every 2–3 days. If bounce rate exceeds 2%, pause increases for 2 days. Maintain a reply rate above 5%.

Phase 3 (Days 15–21): Reach 50 emails/day, cold prospects up to 80% of volume

Continue warmup emails at 20% of volume. Run inbox placement tests every other day. If any metric degrades, reduce volume by 30% for 3 days.

Never increase daily volume by more than 20% in a single day — at any stage

Sudden spikes in sending volume are a primary spam signal. Gradual, consistent growth is what builds a healthy sender reputation.

Keep warmup running continuously, even after reaching full volume

Warmup tools provide ongoing positive engagement signals. Turning them off after reaching target volume leaves your domain vulnerable to reputation decay.

Starter plan: Max 50 emails/day from 1 domain, ~25 per mailbox

1 sending domain, 1–2 mailboxes. Split volume evenly. Best for companies testing cold outreach or with a small target market.

Growth plan: Max 150 emails/day across 2–3 domains, ~50–75 per domain

Rotate sending across domains daily. Each domain handles 50–75 emails with 2–3 mailboxes each.

Scale plan: Max 350 emails/day across 3–5 domains, ~70–100 per domain

Use round-robin domain rotation. Have at least one reserve domain warming up in case a primary domain needs to be pulled.

No single mailbox should send more than 40–50 emails/day

Even on shared infrastructure, individual mailbox volume matters. Exceeding this threshold per mailbox increases spam risk regardless of domain-level limits.

Reduce weekend volume by 50–70% (or pause entirely)

B2B prospects rarely check email on weekends. Low engagement on those sends hurts your sender score. Save volume for Monday–Friday.

Taper down over 3–5 days when pausing — don't drop to zero overnight

An abrupt stop looks suspicious to inbox providers. Gradual ramp-down preserves the reputation you've built.

Send plain text only — no HTML, no images, no logos

HTML formatting (even minimal) triggers additional spam filters. Images and tracking pixels add significant spam weight. Plain text reads like a genuine personal email.

Keep emails 50–120 words

Short emails have higher read and reply rates. If you can't say it in 120 words, your pitch needs tightening — not your email.

Maximum 1–2 links per email

More links = more spam signals. Never use URL shorteners (bit.ly, tinyurl). Use your real domain URLs or natural anchor text, not 'Click Here'.

Avoid spam trigger words in subject lines and body

Financial: free, discount, save, lowest price, cash. Urgency: urgent, limited time, expires, last chance, act now. Sales: buy now, click here, guaranteed, no obligation, winner. Formatting: ALL CAPS, excessive exclamation marks, $$$ signs.

Include a simple opt-out line in every email

"If this isn't relevant, just let me know and I'll remove you." This is both a legal requirement (CAN-SPAM, GDPR) and a deliverability best practice. Process all unsubscribes within 24 hours.

Personalize with prospect name, company, and one relevant detail

An email that could have been sent to anyone will be ignored (or reported). Reference something specific: their role, a company announcement, a tech stack detail. One genuine hook beats ten generic lines.

Use a real person's name in the From field, not a company name

"Sarah from Acme" vs "Acme Inc" — the former gets opened, the latter gets filtered. Real names signal real human communication.

Use spintax or multiple template variants across your prospect list

Sending identical emails to hundreds of people is a spam signal. Small variations in phrasing (without changing substance) significantly improve deliverability.

Verify all email addresses before sending (NeverBounce, ZeroBounce, or MillionVerifier)

Aim for an expected bounce rate under 1% after verification. Re-verify lists older than 90 days — emails go stale faster than you think.

Remove role-based emails (info@, support@, sales@, contact@)

Role-based addresses have higher bounce rates and lower engagement. They're often monitored by multiple people or routed to spam automatically.

Remove catch-all domains from your lists

Catch-all domains accept any email address, so verification tools show them as 'valid' — but they often bounce or route to nowhere. They're a hidden bounce risk.

Hard bounce rate must stay under 3% — pause campaign if exceeded

Remove all hard bounces immediately. If you exceed 3%: pause the campaign, re-verify the entire list, check for blacklisting, then resume at 50% volume.

Maintain a master suppression list synced across all sending domains

Unsubscribes and complaints must be suppressed everywhere — not just the campaign they came from. A prospect who unsubscribed from Campaign A must never receive Campaign B.

Process unsubscribe requests within 24 hours (legally required within 10 business days)

Treat unsubscribes as an opportunity to clean your list. A prospect who asked to be removed and then receives more emails will complain — and complaints destroy domain reputation.

Daily: Check warmup dashboard — are all mailboxes active?

A warmup tool that stops silently is a domain reputation ticking clock. Check that it's running, sending, and generating positive responses every day.

Daily: Review campaign metrics — bounce rate, open rate, reply rate

Green thresholds: bounce <1%, open >50%, reply >10%, spam placement <5%. Warning: bounce 1–3%, open 30–50%. Critical (stop sending): bounce >3%, open <20%, spam placement >15%.

Weekly: Run inbox placement test across major providers (GlockApps or Mail-Tester)

Send a test email to a seed list of Gmail, Outlook, Yahoo, and iCloud accounts. Aim for >90% inbox placement. If you're in promotions or spam, investigate before sending more.

Weekly: Check all sending domains against major blacklists (MXToolbox Blacklist Check)

Blacklisting happens fast. If you're listed: immediately pause sending, submit delisting requests, clean your prospect lists, and resume at 25% of previous volume.

Weekly: Review Google Postmaster Tools — domain reputation and spam rate

Target: High reputation, complaint rate <0.05%. Warning: complaint rate 0.05–0.1%. Critical: >0.1% — stop all sending immediately. Google will penalize domains that stay above 0.1%.

Weekly: Verify DNS records are still valid (SPF, DKIM, DMARC)

DNS records can be accidentally overwritten during domain migrations or when IT teams make changes. A broken DKIM record silently destroys deliverability.

Weekly: Audit prospect list quality — check data source and re-verify as needed

Lists age quickly. A list that was 98% valid three months ago might be 92% valid today. Budget for re-verification at 90-day intervals on active campaigns.