Email Deliverability: Making Sure Your Emails Reach the Inbox

You've crafted the perfect email, but it means nothing if it lands in spam. Email deliverability is the art and science of getting your emails into recipients' inboxes. Let's explore what affects deliverability and how to improve it.

What is Email Deliverability?

Deliverability is the measure of how successfully your emails reach recipients' inboxes (not spam folders). It's affected by three main factors:

Authentication

Proving you're who you say you are

Reputation

Your sending history and trustworthiness

Content

What you say and how you say it

Authentication: The Foundation

Email authentication is the technical foundation of deliverability. Without it, mailbox providers have no way to trust your emails are legitimate.

Quick Reference: Check our Email Security Basics guide for detailed setup instructions for SPF, DKIM, and DMARC.

Authentication Checklist

  • SPF: Publish a record listing all your sending IPs and services
  • DKIM: Sign all outgoing emails with your domain's private key
  • DMARC: Set policy to at least p=quarantine, ideally p=reject
  • Alignment: Ensure your "From" domain matches SPF/DKIM domains

Reputation: Your Email Credit Score

Your sending reputation is like a credit score for email. Mailbox providers track your sending behavior and use it to decide whether to trust future emails.

Factors Affecting Reputation

Factor Good Bad
Bounce Rate < 2% > 5%
Spam Complaints < 0.1% > 0.3%
Spam Trap Hits 0 Any
Engagement Rate > 20% opens < 5% opens

Types of Reputation

  • IP Reputation: Based on the sending server's IP address. Shared IPs carry shared risk.
  • Domain Reputation: Based on your domain's sending history. Follows your domain everywhere.
  • User Reputation: Some providers track reputation at the individual email address level.
New Domain Warning: New domains have no reputation, which means lower trust. "Warm up" new domains by gradually increasing sending volume over 4-8 weeks.

List Hygiene: Quality Over Quantity

A clean email list is essential for good deliverability. Sending to bad addresses damages your reputation fast.

List Hygiene Best Practices

  1. Use double opt-in: Require subscribers to confirm their email address
  2. Remove bounces immediately: Never retry hard bounces
  3. Clean inactive subscribers: Remove contacts who haven't engaged in 6-12 months
  4. Never buy lists: Purchased lists are full of spam traps and unengaged contacts
  5. Make unsubscribing easy: Hidden unsubscribe links lead to spam complaints

Understanding Spam Traps

Spam traps are email addresses used to identify senders with poor list practices:

  • Pristine traps: Addresses that never signed up for anything - hitting these is very bad
  • Recycled traps: Old addresses repurposed as traps - indicates you have stale lists
  • Typo traps: Common misspellings (gmal.com, yahooo.com) - indicates no validation

Content: What You Say Matters

Even with perfect authentication and reputation, poor content can land you in spam.

Content Red Flags

  • ALL CAPS subjects or excessive punctuation!!!
  • Spam trigger words (FREE, ACT NOW, LIMITED TIME)
  • Image-only emails with no text
  • Mismatched display text and URLs
  • URL shorteners (bit.ly, tinyurl)
  • Too many links or images

Content Best Practices

  • Maintain a healthy text-to-image ratio (60% text, 40% images)
  • Use your actual domain for links, not redirects
  • Include a plain text version alongside HTML
  • Keep subject lines under 50 characters
  • Always include your physical mailing address (required by law)

Technical Setup for Deliverability

DNS Records

  • Reverse DNS (PTR): Your sending IP should have a PTR record pointing to your domain
  • MX Records: Even if you only send, having MX records looks more legitimate
  • HELO/EHLO: Configure your mail server's identity to match your domain

Sending Infrastructure

  • Dedicated IPs: For high-volume senders, use dedicated IPs you control
  • IP Warming: Gradually increase volume on new IPs
  • Segmentation: Separate transactional from marketing email infrastructure

Monitoring Your Deliverability

You can't improve what you don't measure. Set up these monitoring systems:

Key Metrics to Track

  • Inbox Placement Rate: Percentage of emails reaching inbox vs spam
  • Bounce Rate: Hard bounces (invalid) and soft bounces (temporary)
  • Spam Complaint Rate: People marking your email as spam
  • Engagement Metrics: Open rates, click rates, reply rates

Feedback Loops

Sign up for Feedback Loops (FBLs) with major providers to receive notifications when users mark your email as spam:

  • Microsoft SNDS and JMRP
  • Google Postmaster Tools
  • Yahoo Complaint Feedback Loop
Pro Tip: Set up DMARC aggregate reports (rua=) to receive daily summaries of who's sending email as your domain and whether it's passing authentication.

Deliverability Troubleshooting

If You're Landing in Spam

  1. Check authentication (SPF, DKIM, DMARC) is properly configured
  2. Verify your IP/domain isn't on any blacklists
  3. Review recent content for spam triggers
  4. Check your bounce and complaint rates
  5. Reduce sending volume temporarily
  6. Focus on your most engaged subscribers first

Common Issues and Fixes

Problem Likely Cause Solution
Gmail spam folder Low engagement, authentication issues Check Postmaster Tools, improve content
Bouncing everywhere IP blacklisted Check MXToolbox, request delisting
Slow delivery Throttling due to reputation Reduce volume, warm up slowly
DMARC failures Third-party sender not configured Add to SPF, configure DKIM

Test Your Email Setup

Check your domain's email security configuration and get recommendations for improvement:

Check Your Email Security →

Related Articles

Email Security Basics → Advanced Authentication →