How to Improve Email Deliverability: 10 Proven Strategies

What is Email Deliverability?

Email deliverability measures your ability to successfully land emails in subscribers' inboxes (not spam folders, not bounced). It's determined by your sender reputation, authentication setup, list quality, and content.

Deliverability vs. Delivery Rate

Understanding the difference is crucial:

• Delivery Rate: % of emails accepted by recipient mail servers (not bounced)
• Deliverability Rate: % of delivered emails reaching the inbox (not spam)

Example: You might have 98% delivery rate but only 80% deliverability if 18% land in spam. Deliverability is what matters because spam emails don't get opened.

📚 Comprehensive Guide: Master all aspects of deliverability in our complete email deliverability pillar guide →

1. Set Up Email Authentication (SPF, DKIM, DMARC)

Email authentication proves you're a legitimate sender and prevents spoofers from using your domain. It's the foundation of good deliverability.

The Three Authentication Protocols

SPF (Sender Policy Framework)

SPF lists which mail servers are authorized to send email from your domain. ISPs check this list to verify senders.

• Setup: Add TXT record to your domain's DNS
• Example: "v=spf1 include:_spf.igsendmail.com ~all"
• Impact: Prevents domain spoofing, improves inbox placement

DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to your emails that proves they weren't tampered with during transit.

• Setup: Add public key to DNS, ESP signs emails with private key
• Benefit: Verifies email integrity and sender identity
• Result: Higher trust from ISPs

DMARC (Domain-based Message Authentication)

DMARC tells ISPs what to do with emails that fail SPF/DKIM checks and provides feedback reports.

• Policy levels: None (monitor), Quarantine (spam), Reject (block)
• Reports: Receive daily reports on authentication failures
• Protection: Prevents phishing and brand impersonation

2. Maintain Excellent List Hygiene

List quality directly impacts deliverability. Clean lists have higher engagement and better sender reputation.

Regular List Cleaning Practices

Remove Hard Bounces Immediately

Hard bounces are invalid email addresses that will never receive email. Sending to them damages your reputation.

• Remove hard bounces after first attempt
• Never email hard bounces again
• Keep bounce rate under 2%

Manage Soft Bounces

Soft bounces are temporary issues (full inbox, server down). Handle strategically:

• Retry 3-5 times over 7-10 days
• Remove if still bouncing after retry period
• Track patterns by domain to identify issues

Sunset Inactive Subscribers

Subscribers who haven't engaged in 6-12 months hurt your metrics and reputation.

• Identify: No opens/clicks in 6+ months
• Re-engage: Send win-back campaign first
• Remove: Unsubscribe if still inactive
• Benefit: Improves engagement rates and sender score

Handle Spam Complaints Promptly

• Remove complainers from all lists immediately
• Keep complaint rate under 0.1%
• Investigate patterns if complaints spike

3. Use Double Opt-In

Double opt-in requires subscribers to confirm their email address before being added to your list. It's the gold standard for list quality.

Why Double Opt-In Improves Deliverability

• Validates addresses: Confirms emails are real and accessible
• Confirms intent: Ensures subscribers actually want your emails
• Reduces typos: Catches misspelled email addresses
• Prevents abuse: Stops malicious signups with fake/other's emails
• Higher engagement: Double opt-in lists have 2x higher engagement
• Legal compliance: Demonstrates explicit consent (GDPR requirement)

Implementing Double Opt-In

1. Signup: User submits email address
2. Confirmation email: Send immediate email with confirmation link
3. Click to confirm: User clicks link to verify
4. Welcome email: Send welcome message after confirmation

4. Maximize Engagement Rates

ISPs track how subscribers interact with your emails. High engagement signals quality content and improves deliverability.

Tactics to Boost Engagement

Segment Your List

• Send relevant content to specific groups
• Segment by: interests, behavior, location, purchase history
• Result: 3x higher engagement than broadcast emails

Personalize Content

• Use subscriber's name in subject line and greeting
• Reference past purchases or browsing behavior
• Recommend products based on preferences
• Impact: 6x higher transaction rates

Write Compelling Subject Lines

• Keep under 50 characters for mobile
• Create curiosity without clickbait
• Use personalization and urgency strategically
• A/B test consistently

Optimize Send Times

• B2B: Tuesday-Thursday, 10am-2pm
• B2C: Weekend mornings, weekday evenings
• Test your audience: Optimal times vary by industry
• Use send-time optimization: Deliver when each subscriber is most active

Make Unsubscribing Easy

• Clear, visible unsubscribe link in every email
• One-click unsubscribe (no login required)
• Process immediately (within 10 days per CAN-SPAM)
• Better to lose subscriber than get spam complaint

5. Optimize Email Content for Spam Filters

Spam filters analyze your content. Avoid triggers while maintaining effective messaging.

Content Red Flags to Avoid

Spammy Words and Phrases

• Avoid: "Free", "Act now", "Limited time", "Guaranteed", "No credit card"
• Issue: Overuse triggers spam filters
• Alternative: Use specific, honest language

ALL CAPS and Excessive Punctuation

• Don't: "BUY NOW!!!", "FREE SHIPPING TODAY!!!!"
• Do: "Shop today's sale" or "Free shipping on orders $50+"

Image-to-Text Ratio

• Aim for 60% text, 40% images
• Never send image-only emails
• Always include alt text for images
• Text should convey full message if images don't load

Link Quality

• Use reputable domains only
• Avoid URL shorteners (bit.ly, tinyurl)
• Don't hide links with misleading anchor text
• Limit total links to 3-5 per email

Content Best Practices

• Write conversational, authentic copy
• Focus on providing value first
• Use proper HTML formatting
• Include plain text version
• Test emails with spam checker tools

6. Send Consistently

Consistent sending patterns build trust with ISPs. Erratic sending (especially sudden spikes) looks suspicious.

Why Consistency Matters

• ISP trust: Regular patterns signal legitimate sender
• Subscriber expectations: Consistency builds habit and recognition
• Reputation stability: Steady metrics are easier to maintain
• Spam avoidance: Sudden volume spikes trigger filters

Building Consistency

• Pick a schedule you can maintain long-term
• Send same day/time each week/month
• Gradually increase volume (don't blast cold lists)
• Warm up new domains/IPs slowly
• Plan campaigns in advance

Warming Up New Domains or IPs

When starting fresh or switching platforms:

• Week 1: 50-100 emails to most engaged subscribers
• Week 2: 500-1,000 emails
• Week 3: 2,000-5,000 emails
• Week 4+: Double volume until full list

7. Monitor Your Sender Reputation

Your sender reputation is like a credit score for email. ISPs use it to decide inbox vs. spam placement.

What Affects Sender Reputation

• Bounce rate: Target <2%
• Spam complaint rate: Target <0.1%
• Engagement rates: Opens, clicks, replies
• Authentication: SPF/DKIM/DMARC setup
• Blacklists: Presence on spam databases
• Sending patterns: Consistency and volume
• List quality: Fresh, engaged subscribers

Tools to Monitor Reputation

• Google Postmaster Tools: Gmail-specific reputation and placement data
• Microsoft SNDS: Outlook/Hotmail reputation score
• SenderScore: Overall reputation score (0-100, aim for 90+)
• MXToolbox: Check blacklist status
• GlockApps/EmailOnAcid: Deliverability testing services

Recovering from Poor Reputation

If your reputation is damaged:

1. Stop sending temporarily: Pause 2-3 days
2. Clean your list aggressively: Remove all inactive/invalid
3. Implement all authentication: SPF, DKIM, DMARC
4. Segment best subscribers: Re-engage most active first
5. Start slow: Warm up like a new sender
6. Monitor closely: Watch metrics daily
7. Be patient: Recovery takes 4-8 weeks