Email Deliverability Best Practices

Getting your emails into the inbox (not spam) is critical. Learn proven strategies to maximize deliverability and maintain strong sender reputation.

What is Deliverability?

Deliverability is the percentage of your emails that reach the inbox (vs. spam folder or bounced). Industry average is 75-85%. With proper setup and practices, you can achieve 95%+.

Technical Setup (Critical)

SPF, DKIM, DMARC Records

These DNS records authenticate your domain and prove you're a legitimate sender:

SPF (Sender Policy Framework)

Lists authorized servers that can send email from your domain.

Setup: Add TXT record to your domain's DNS. For Gmail: include:_spf.google.com

DKIM (DomainKeys Identified Mail)

Cryptographic signature that proves email wasn't tampered with.

Setup: Add TXT record with public key. Gmail/G Suite enables automatically.

DMARC (Domain-based Message Authentication)

Tells receiving servers what to do if SPF/DKIM checks fail.

Setup: Add TXT record: v=DMARC1; p=quarantine; rua=mailto:postmaster@yourdomain.com

Custom Domain (Highly Recommended)

Content Best Practices

Avoid Spam Trigger Words

These words and phrases frequently trigger spam filters:

❌ Money/Urgency

Free, $$$, Make money fast, Act now, Limited time, Urgent, Click here now, Guarantee, No risk

❌ Excessive Punctuation

CAPS!!!!, Multiple exclamation points!!!!!, Dear friend!!!!

❌ Suspicious Language

Act immediately, As seen on, Cancel any time, Check or money order, Dear friend, Earn extra cash

Email Structure

  • Text-to-image ratio: At least 60% text, max 40% images
  • Link count: Keep under 5 links per email
  • HTML cleanliness: Avoid messy code (plain text is best for cold emails)
  • Personalization: Use contact's name and company (not "Dear Sir/Madam")

Subject Line Tips

✅ Good: "Quick question about Acme's Q4 growth"

✅ Good: "Following up on our conversation"

❌ Bad: "FREE TRIAL - MAKE MONEY NOW!!!"

❌ Bad: "Re: Your recent inquiry" (when there was no inquiry)

Sending Behavior

Start Slow (Critical for New Domains)

Gradually increase volume over 4-6 weeks:

  • Week 1: 50 emails/day
  • Week 2: 100 emails/day
  • Week 3: 200 emails/day
  • Week 4: 400 emails/day
  • Week 5-6: Up to provider limit (500-2,000/day)

Daily Send Limits

  • Gmail free: 500/day (conservative: use 400/day)
  • Google Workspace: 2,000/day (conservative: use 1,500/day)
  • Outlook/Yahoo: Varies, typically 300-500/day
  • Custom SMTP: Check with your provider

Timing Recommendations

  • Best days: Tuesday-Thursday (avoid Monday morning inbox overload, Friday afternoon checkout)
  • Best times: 10 AM - 3 PM in recipient's timezone
  • Avoid: Weekends, holidays, after 5 PM

List Hygiene

Validate Email Addresses

Use email verification services before importing:

  • ZeroBounce: Comprehensive validation + spam trap detection
  • NeverBounce: Real-time validation API
  • Hunter.io: Email finder + verification
  • Target: 95%+ valid rate before sending

Remove Problem Contacts

  • Hard bounces: Remove immediately (invalid addresses)
  • Soft bounces: Retry 2-3 times, then remove
  • Unsubscribes: Honor immediately (WarmOpener does this automatically)
  • Spam complaints: Remove immediately and investigate why

Monitoring & Metrics

Key Metrics to Track

  • Bounce rate: Should be < 2% (ideal: < 0.5%)
  • Spam complaint rate: Should be < 0.1%
  • Unsubscribe rate: Typical: 0.2-0.5%
  • Open rate: B2B average: 15-25%
  • Reply rate: Good cold outreach: 5-10%

Tools for Monitoring

  • Google Postmaster Tools: Monitor domain reputation for Gmail recipients
  • Microsoft SNDS: Sender reputation for Outlook/Hotmail
  • MXToolbox: Check if your domain/IP is blacklisted
  • Mail-Tester: Test deliverability before sending campaigns

If You End Up in Spam

Immediate Actions

  1. Pause campaigns - Stop sending immediately
  2. Check blacklists - Use MXToolbox to see if you're listed
  3. Review recent emails - Identify what might have triggered spam filters
  4. Check bounce rate - High bounces hurt sender reputation
  5. Warm up slowly - Restart with low volume after fixing issues

Long-term Fixes

  • Verify SPF/DKIM/DMARC are correctly configured
  • Clean your contact list (remove invalid/old addresses)
  • Improve email content (less salesy, more personalized)
  • Reduce sending volume and rebuild reputation
  • Consider using a different subdomain (e.g., outreach.yourdomain.com)

⚠️ Critical Warning

Sending to purchased or scraped email lists will destroy your sender reputation. Only send to contacts who have some connection to you (visited your website, attended webinar, LinkedIn connection, etc.). Cold email is legal, but blasting random lists is not effective and will get you blacklisted.

💡 Pro Tip

Send a test email to a Gmail and Outlook account you control before launching campaigns. Check if it lands in inbox or spam. If spam, revise content before sending to your list. This simple test can save your campaign.

Need help? Email Support
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