$ man how-to/email-deliverability-checklist-2026

CODE

The pre-launch checklist. Do not skip any step. 1. Buy 3-5 secondary domains (never send cold email from your primary domain) 2. Set up Google Workspace or Microsoft 365 mailboxes on each domain (2-3 per domain) 3. Add SPF record to DNS for each domain 4. Enable DKIM signing in your email provider admin panel and add DKIM records to DNS 5. Add DMARC record to DNS (start with p=none, upgrade to p=quarantine after 2 weeks) 6. Verify all records at MXToolbox.com or mail-tester.com (score should be 9/10 or higher) 7. Start warmup on every mailbox (minimum 14 days, ideally 21-30 days) 8. Set up Google Postmaster Tools for each domain to monitor reputation 9. Create a custom tracking domain for your cold email tool (avoids shared tracking domain blacklists) 10. Test send to your own Gmail, Outlook, and Yahoo accounts to verify inbox placement

FORMULA

These limits keep your domains healthy: 11. Maximum 25-30 cold emails per mailbox per day (plus 20-30 warmup emails) 12. Ramp volume gradually: 5/day week 1, 10/day week 2, 15/day week 3, 20-25/day week 4 13. Rotate across all domains and mailboxes (your cold email tool handles this automatically) 14. Keep bounce rate below 3% (above 5% = pause and clean your list immediately) 15. Keep spam complaint rate below 0.1% (Gmail hard limit is 0.3%)

PATTERN

What you write affects where it lands. Content rules: Avoid spam trigger words in subject lines: "free", "guaranteed", "act now", "limited time", "click here." These are not automatic spam triggers, but they increase spam filter sensitivity. Keep emails short. 50-125 words performs best for cold email. Long emails signal marketing rather than personal communication. Limit links. One link maximum in the email body (your CTA). Zero links in the first email of a sequence performs even better. Spam filters flag emails with multiple links. No images in cold email. Images trigger spam filters and look like marketing emails. Pure text looks like a real person writing to another person. Plain text format. No HTML formatting, no bold, no colors. If your cold email looks like a newsletter, it gets filtered like a newsletter. Include an unsubscribe mechanism. A simple line at the bottom: "If this is not relevant, let me know and I will not follow up." This is legally required and reduces spam complaints. Avoid URL shorteners. bit.ly and similar services are abused by spammers. Use your full domain URL or a custom tracking domain.

PATTERN

Deliverability degrades if you stop paying attention. Weekly checks: Google Postmaster Tools: check domain reputation (should be "High" or "Medium"). If it drops to "Low", pause cold sending immediately and investigate. Bounce rate by campaign: any campaign above 3% bounce rate needs list cleaning. Pull the bounced addresses, identify the pattern (all from one company? old data source? specific domain?), and fix the source. Spam complaint monitoring: check in your cold email tool. Even one complaint per 1,000 emails (0.1%) is a warning sign. Investigate which emails triggered complaints. Open rates as deliverability proxy: if your open rates drop below 30%, you likely have a deliverability problem. Healthy cold email open rates are 45-65%. Below 30% means emails are landing in spam. Warmup health: check that warmup is still running on all accounts. Some tools pause warmup automatically when sending volume is high. Keep warmup running continuously. Domain age: track how old each domain is. Domains under 30 days old should send at reduced volume. Domains under 90 days old should not exceed 20 emails/day.

PRO TIP

If a domain gets flagged or inbox placement drops: 1. Pause all cold sending from the affected domain immediately 2. Keep warmup running (or increase warmup volume slightly) 3. Check Google Postmaster Tools for specific issues 4. Review recent campaigns for high bounce rates, spam complaints, or content issues 5. Wait 7-14 days with only warmup (no cold email) to rebuild reputation 6. Resume cold sending at 50% volume and ramp back up gradually over 2 weeks If a domain is fully burned (reputation stays "Bad" after 30 days of rest), retire it. Remove all mailboxes, stop warmup, and replace with a new domain. Domain burning is normal in cold outbound - treat domains as consumable infrastructure, not permanent assets. The prevention: rotate domains before they burn. If you have 5 domains, use 3 actively and keep 2 on warmup-only as backups. Rotate the active set every 60-90 days. This keeps every domain fresh and prevents any single domain from accumulating too much cold sending history.