Email Deliverability Best Practices for 2024 and Beyond

Email deliverability isn't just about whether your emails arrive - it's about ensuring they land in the inbox, not the spam folder. With increasingly sophisticated filtering by major providers, getting deliverability right has never been more important.

The Deliverability Equation

Inbox placement depends on multiple factors:

Deliverability = Authentication + Reputation + Content + Engagement

Let's break down each component.

1. Technical Foundation

Email Authentication Trifecta

Every domain sending email needs these three protocols properly configured:

SPF: Authorizes sending IP addresses

v=spf1 include:_spf.google.com include:sendgrid.net -all

DKIM: Cryptographic signature proving authenticity

selector._domainkey.example.com TXT "v=DKIM1; k=rsa; p=..."

DMARC: Policy for handling authentication failures

v=DMARC1; p=reject; rua=mailto:dmarc@example.com

Infrastructure Requirements

• Valid PTR Records: Reverse DNS must resolve to your sending domain
• Dedicated IPs: For high-volume senders, dedicated IPs give you control over reputation
• TLS Encryption: All email transmission should be encrypted
• Proper DNS Configuration: MX records, A records, and authentication records all correct

2. Sender Reputation

Your sender reputation is like a credit score for email. It determines how mailbox providers treat your messages.

IP Reputation

Your sending IP address accumulates a reputation based on:

• Volume and consistency of sending
• Spam complaint rates
• Bounce rates
• Spam trap hits
• Blacklist presence

Domain Reputation

Increasingly, reputation is tied to your domain:

• Historical sending patterns
• Authentication pass rates
• User engagement signals
• Complaint history

Warming Up New IPs/Domains

Never go from zero to full volume immediately. Follow a warm-up schedule:

Maintaining Good Reputation

• Keep spam complaints under 0.1% (0.3% maximum)
• Maintain bounce rates under 2%
• Never purchase email lists
• Remove inactive subscribers
• Honor unsubscribes immediately

3. List Quality and Hygiene

Building Quality Lists

Do:

• Use confirmed opt-in (double opt-in)
• Set expectations at signup
• Collect emails through owned properties
• Segment by interest and engagement

Don't:

• Buy or rent email lists
• Scrape emails from websites
• Add people without consent
• Import old, stale lists

Ongoing List Maintenance

Remove these addresses immediately:

• Hard bounces (invalid addresses)
• Repeated soft bounces
• Spam complaints
• Unsubscribes

Re-engagement or Removal:

• No opens in 6 months → Re-engagement campaign
• No engagement after re-engagement → Remove
• No opens in 12 months → Remove

Spam Traps

Pristine Traps: Addresses that never opted in to anything

• Only way to hit: buying lists or scraping

Recycled Traps: Abandoned addresses turned into traps

• Hit by keeping old addresses without re-engaging

4. Content Best Practices

Subject Lines

• Keep under 50 characters
• Avoid spam trigger words (FREE!!!, Act Now, etc.)
• Don't use ALL CAPS
• Skip excessive punctuation!!!
• Be relevant and honest

Email Body

Structure:

• Clear hierarchy with headers
• Mobile-responsive design
• Balance text and images (not image-only)
• Alt text for all images

Content:

• Relevant to subscriber interests
• Consistent with subject line promise
• Clear call to action
• Easy-to-find unsubscribe link

Technical Elements

• Valid HTML
• Plain text version included
• Proper character encoding
• No broken links
• Images hosted on reputable domains

5. Engagement Metrics

Modern spam filters heavily weight user engagement:

Positive Signals

• Opens (though less reliable with privacy features)
• Clicks
• Replies
• Moving from spam to inbox
• Adding to contacts
• Forwarding

Negative Signals

• Deleting without reading
• Marking as spam
• Ignoring consistently
• Moving to spam folder

Improving Engagement

Segmentation:

• Send relevant content to each segment
• Adjust frequency by engagement level
• Personalize based on behavior

Timing:

• Test different send times
• Consider subscriber time zones
• Avoid over-sending

Content:

• A/B test subject lines
• Provide value in every email
• Make emails easy to scan

6. Monitoring and Analytics

Key Metrics to Track

Tools for Monitoring

Google Postmaster Tools:

• Spam rate for Gmail
• Domain reputation
• Authentication status
• Delivery errors

MailSentinel:

• DMARC report analysis
• Authentication monitoring
• SPF/DKIM/DMARC status
• Real-time alerts

Blacklist Monitoring:

• Check major blacklists regularly
• Set up automated monitoring
• Act immediately if listed

7. Handling Deliverability Issues

Diagnosing Problems

Sudden Drops:

1. Check authentication (SPF, DKIM, DMARC)
2. Review recent content changes
3. Check for blacklist listings
4. Analyze complaint rates
5. Review sending volumes

Gradual Decline:

1. Audit list quality
2. Check engagement trends
3. Review competitor activity
4. Analyze inbox vs. spam placement

Recovery Strategies

Blacklist Removal:

1. Identify the cause
2. Fix the underlying issue
3. Request delisting
4. Document your remediation

Reputation Recovery:

1. Reduce volume temporarily
2. Send only to engaged users
3. Focus on generating positive engagement
4. Gradually rebuild

8. Special Considerations

Transactional vs. Marketing Email

Transactional Email:

• Order confirmations, password resets, etc.
• Generally exempt from unsubscribe requirements
• Send from dedicated infrastructure
• Still needs authentication

Marketing Email:

• Newsletters, promotions, etc.
• Must have unsubscribe option
• Subject to engagement-based filtering
• Requires explicit consent

B2B vs. B2C

B2B:

• Often sent to corporate domains
• May face stricter security filters
• Smaller volumes, higher stakes
• Relationship-based engagement

B2C:

• Gmail, Yahoo, Outlook dominate
• Subject to user engagement signals
• Higher volumes
• Content-driven engagement

Cold Email Deliverability

Cold email (outbound sales) faces unique challenges and requires special attention to authentication and deliverability.

Why Authentication is Critical

Cold Email Challenges:

• No prior relationship with recipients
• Higher spam scrutiny from providers
• Stricter filtering than transactional email
• Reputation starts at zero
• Volume requirements for scale

Without Proper Authentication:

• 70% to 90% rejection rate
• 5% to 15% inbox placement
• Campaigns fail before they start

With Proper Authentication:

• 80% to 95% inbox placement
• 16x to 19x improvement in delivery
• Campaigns can scale successfully

Cold Email Authentication Setup

Required Setup:

1. SPF - Include your cold email tool (Instantly, Smartlead, Email Bison, etc.)
2. DKIM - Enable signing from your tool
3. DMARC - Set up monitoring and policy

Domain Strategy:

• Use dedicated subdomain (e.g., sales.yourdomain.com)
• Isolate cold email reputation
• Protect main domain

Tool-Specific SPF Includes:

• Instantly.ai: include:spf.instantly.ai
• Smartlead.ai: include:spf.smartlead.ai
• Email Bison: include:spf.emailbison.com
• Lemlist: include:spf.lemlist.com

Cold Email Best Practices

Domain Warmup:

• Week 1: 10-20 emails/day
• Week 2: 30-50 emails/day
• Week 3: 75-100 emails/day
• Week 4: 150-200 emails/day
• Gradually increase to target volume

List Quality:

• Valid email addresses only
• No purchased lists
• Regular list cleaning
• Verify addresses before sending

Content Quality:

• Personalized messages
• Relevant content
• Clear value proposition
• Professional tone
• Avoid spam triggers

Monitoring:

• DMARC pass rate (target: 95%+)
• Inbox placement (target: 80%+)
• Open rate (target: 20%+)
• Reply rate (target: 5%+)
• Spam complaints (must be <0.3%)

Resources:

• Cold Email Deliverability Guide - Complete guide
• Cold Email Authentication Setup - Step-by-step
• Tool-Specific Guides - Instantly, Smartlead, Email Bison

Action Checklist

Weekly

• Review delivery and engagement metrics
• Check spam complaint rates
• Monitor authentication status
• Process bounces and unsubscribes

Monthly

• Audit email authentication records
• Review list growth and churn
• Analyze segment performance
• Check blacklist status

Quarterly

• Deep list hygiene review
• Re-engagement campaigns for inactive
• Authentication and infrastructure audit
• Deliverability strategy review

Conclusion

Email deliverability is a continuous effort, not a one-time setup. By focusing on authentication, reputation, list quality, content, and engagement, you build a sustainable email program that consistently reaches the inbox.

Monitor your email authentication with MailSentinel and stay ahead of deliverability issues.