Email deliverability is the foundation of every successful outreach campaign. If your emails don't reach the inbox, nothing else matters. Here's a complete 20-point checklist to audit right now.
Domain & Authentication (Must-Haves)
1. SPF Record
Your SPF (Sender Policy Framework) record tells receiving mail servers which IP addresses are authorized to send email on behalf of your domain. Without it, you'll fail authentication checks.
Check: Run your domain through mxtoolbox.com/spf.aspx. You should see "SPF Record Found" with a passing result.
Fix: Add a TXT record to your DNS: 'v=spf1 include:_spf.google.com ~all' (adjust based on your ESP).
2. DKIM Signature
DKIM (DomainKeys Identified Mail) adds a cryptographic signature to your emails proving they weren't tampered with in transit.
Check: Send a test email to mail-tester.com and check the DKIM result.
Fix: Enable DKIM signing in your ESP or email client settings. Most ESPs generate the DNS record for you.
3. DMARC Policy
DMARC tells receiving servers what to do when SPF/DKIM fail — reject, quarantine, or do nothing. Without DMARC, failing emails may still reach inboxes (bad for security) and ISPs penalize senders without it.
Minimum: 'v=DMARC1; p=none; rua=mailto:[email protected]'
Recommended: 'v=DMARC1; p=quarantine; pct=100'
4. Custom Tracking Domain
If your cold email tool uses a shared tracking domain for open and click tracking, your deliverability is tied to every other user on that domain. Set up a custom tracking subdomain.
Example: 'track.yourdomain.com' instead of 'tracking.yourtool.com'
5. Dedicated Sending Domain
Never send cold email from your primary company domain. One spam complaint can damage your entire organization's email reputation.
Recommended pattern: Use 'getcompany.com', 'mailcompany.com', or 'company-mail.com' for cold outreach.
Sender Reputation
6. Check Your IP Reputation
If you're sending via a shared IP pool (most SMTPs are), check if any IPs you're sending from are blacklisted.
Tools: MXToolbox Blacklist Check, Spamhaus, Barracuda Reputation
7. Warm Up New Accounts
Any new email account or domain needs a 4–8 week warm-up period before heavy sending. See our full email warm-up guide for details.
8. Check Your Domain Age
Domains under 3 months old are treated with extreme suspicion. If you're using a brand new domain, extend your warm-up period and start with very low send volumes.
9. Monitor Google Postmaster Tools
If you send to Gmail addresses (most B2B email goes to Google Workspace), set up Google Postmaster Tools. It shows your domain reputation and spam rate directly from Google's perspective.
Setup: postmaster.google.com — add your domain and verify ownership via DNS.
10. Review Spam Complaint Rate
Your spam complaint rate should stay below 0.1%. Above 0.3% and major ISPs will start aggressively filtering your emails. Track this in Google Postmaster Tools.
List Hygiene
11. Verify Email Addresses Before Sending
Sending to invalid addresses = bounces. High bounce rates destroy reputation. Use a list verification service before loading any new list.
Target: Keep bounce rate below 2%.
12. Remove Hard Bounces Immediately
Any address that hard bounces (invalid address, domain doesn't exist) must be removed from your list permanently. Never retry a hard bounce.
13. Respect Unsubscribes Within 10 Days (CAN-SPAM)
You're legally required to honor unsubscribe requests within 10 business days. OutreachBin handles this automatically, but make sure you're not importing suppressed contacts from external sources.
14. Don't Buy Email Lists
Purchased lists are filled with spam traps, invalid addresses, and people who have never heard of you. One spam trap hit can get your entire domain blacklisted. Always build lists from verified sources.
15. Check for Spam Traps
Even organically-built lists can accumulate spam traps over time. If a list is older than 6 months, run it through a spam trap checker before sending.
Email Content
16. Test With Mail-Tester.com
Send a test email to your mail-tester.com address and review your score. Aim for 9+/10. The tool shows exactly which content elements are triggering spam filters.
17. Avoid Spam Trigger Words
Words like FREE, GUARANTEED, NO RISK, CLICK HERE, ACT NOW, and MAKE MONEY send red flags to spam filters. Use natural language instead.
18. Balance Text-to-Image Ratio
Emails that are 100% images or 100% text both look suspicious. The sweet spot is 80% text, 20% images (or no images for cold email — plain text converts better anyway).
19. Limit Links
Each link in a cold email increases spam score. For cold outreach, one link maximum — your CTA. No social icons, no multiple URLs, no "unsubscribe" in the footer for cold email (include opt-out language in text instead).
20. Check Mobile Rendering
Over 60% of emails are opened on mobile. Preview your email on mobile before sending. An email that breaks on mobile = immediate delete.
Quick Audit Summary
Run this checklist before every new domain, every new campaign, and quarterly on your active sending accounts. Deliverability isn't a one-time fix — it's ongoing maintenance.
OutreachBin's InboxWarm handles items 7–8 automatically. The remaining checks ensure your foundation is solid before you scale.