Email Deliverability

Ensuring Your Emails Reach the Inbox

Email deliverability is the ability to get your emails into recipients' inboxes consistently, rather than being filtered to spam folders or rejected entirely. It's the culmination of all the technical and reputation factors we've discussed in other sections.

The Deliverability Challenge

ISPs and email providers are constantly improving their filtering algorithms to protect users from unwanted messages. This creates a challenge for legitimate senders who need to ensure their messages aren't caught in these filters.

Successful email deliverability requires a holistic approach that addresses:

  • Technical factors: Authentication, infrastructure, and proper configuration
  • Reputation factors: Sender history, IP and domain reputation
  • Content factors: Message quality, relevance, and engagement
  • List hygiene: Maintaining clean recipient lists and handling bounces

Email Deliverability Simulator

Test your email content to see how it might be evaluated by spam filters. Edit the sample email and analyze it for potential deliverability issues.

Email Deliverability Simulator

Edit the email content below and analyze it for potential deliverability issues.

Analysis Results:

Click "Analyze Deliverability" to check your email

This is a simplified simulation. Actual email filtering systems use hundreds of factors and machine learning algorithms to determine email placement.

Bounce Handling

Proper bounce management is crucial for maintaining good deliverability.

Hard Bounces

Permanent delivery failures (invalid address, domain doesn't exist). Remove these addresses immediately from your lists.

Soft Bounces

Temporary delivery issues (mailbox full, server down). Retry delivery but remove after multiple consecutive failures.

Bounce Rate Thresholds

Keep hard bounce rates below 2% and total bounce rates below 5% to maintain good deliverability.

Feedback Loops

Feedback loops (FBLs) provide notifications when recipients mark your emails as spam.

How FBLs Work

ISPs send notifications to the sender when a user clicks "mark as spam," allowing you to remove these users from your lists.

Major FBL Providers

Gmail, Yahoo, Microsoft, AOL, and others offer feedback loops that senders can register for.

Complaint Rate Thresholds

Keep complaint rates below 0.1% (1 complaint per 1,000 emails) to maintain good deliverability.

Email Throttling and Rate Limiting

Sending too many emails too quickly can trigger rate limits at receiving mail servers, causing temporary blocks or deferrals.

Why Throttling Matters

  • Prevents overwhelming receiving servers
  • Reduces the risk of being flagged as a spammer
  • Allows for better delivery monitoring
  • Helps maintain consistent sending patterns

Throttling Best Practices

  • Implement rate limiting in your sending infrastructure
  • Adjust sending rates based on domain-specific limits
  • Monitor for temporary failures and retry appropriately
  • Gradually increase volume when warming up IPs

Deliverability Best Practices

Technical Setup

  • Implement SPF, DKIM, and DMARC authentication
  • Set up proper reverse DNS (PTR) records
  • Use consistent sending infrastructure
  • Monitor blacklists and address listings promptly
  • Implement TLS encryption for transmission

List Management

  • Use double opt-in for new subscribers
  • Regularly clean your email lists
  • Remove inactive subscribers after re-engagement attempts
  • Process unsubscribes immediately
  • Segment lists for better targeting and engagement

Sending Practices

  • Maintain consistent sending volumes and frequencies
  • Properly warm up new IP addresses
  • Monitor engagement metrics and adjust accordingly
  • Test emails before sending to large audiences
  • Use a recognizable sender name and reply-to address

Content Considerations

  • Create relevant, valuable content for recipients
  • Avoid spam trigger words and excessive punctuation
  • Maintain a good text-to-image ratio
  • Ensure mobile-friendly design
  • Include clear unsubscribe options