Email Deliverability Best Practices

Email deliverability is the cornerstone of successful email communication. Whether you're sending transactional emails, marketing campaigns, or critical business communications, it's essential that your messages reach the intended recipients' inboxes—not their spam folders or, worse, get blocked entirely.

With email providers continuously refining their filtering algorithms to combat spam and protect users, following email deliverability best practices has never been more important. In this comprehensive guide, we'll explore proven strategies to maximize your inbox placement rates and ensure your emails get the attention they deserve.

Understanding Email Deliverability

Before diving into best practices, it's important to understand what email deliverability means and how it differs from delivery.

Email delivery simply means that your email was accepted by the recipient's mail server without bouncing. However, email deliverability refers to where that email lands once accepted—whether it reaches the recipient's inbox, gets filtered to a promotional tab, or ends up in the spam folder.

Multiple factors influence deliverability, including:

• Sender reputation and authentication
• Email infrastructure and configuration
• Content and design of your emails
• Recipient engagement and list quality
• Compliance with email regulations

Let's explore each of these areas in detail to help you maximize your inbox placement rates.

Technical Infrastructure and Authentication

The foundation of good email deliverability starts with proper technical configuration. These technical elements establish your identity as a legitimate sender and help mailbox providers trust your messages.

Implement Proper Email Authentication

Email authentication protocols verify that emails truly come from the domains they claim to be from, helping to prevent spoofing and phishing. Implementing these standards is no longer optional—it's essential for good deliverability.

• SPF (Sender Policy Framework): Specify which mail servers are authorized to send email on behalf of your domain. This prevents spammers from sending emails that appear to come from your domain.
• DKIM (DomainKeys Identified Mail): Add a digital signature to your emails that verifies they weren't altered in transit and proves ownership of the sending domain.
• DMARC (Domain-based Message Authentication, Reporting & Conformance): Build on SPF and DKIM to specify how receiving mail servers should handle emails that fail authentication checks, and receive reports about authentication results.
• BIMI (Brand Indicators for Message Identification): A newer standard that allows brand logos to appear next to authenticated emails in supporting mailboxes, improving recognition and trust.

Use Dedicated IP Addresses for High-Volume Sending

For businesses sending large volumes of email (typically more than 50,000 emails per month), a dedicated IP address offers several advantages:

• Complete control over your sending reputation
• Isolation from other senders who might damage shared IP reputation
• More consistent deliverability metrics
• Easier troubleshooting of deliverability issues

If you use a dedicated IP, remember to "warm it up" by gradually increasing sending volume over several weeks. This helps establish a positive sending reputation before reaching your full volume.

Maintain Proper DNS Records

Ensure your DNS records are correctly configured with:

• Valid A and MX records for your sending domain
• Reverse DNS (PTR) records that match your sending domain
• SPF, DKIM, and DMARC records as discussed above

Incorrect or missing DNS records can trigger spam filters and hurt deliverability.

Sender Reputation and List Quality

Your sender reputation is like a credit score for email—it reflects how mailbox providers view your sending practices and significantly impacts deliverability. Maintaining list quality is a critical component of building a positive reputation.

Build and Protect Your Sender Reputation

• Maintain consistent sending volumes and frequency
• Monitor and minimize bounce rates (aim for below 2%)
• Keep spam complaint rates low (under 0.1% is ideal)
• Send content that recipients engage with positively
• Use a consistent sending infrastructure (domains, IPs, authentication)
• Monitor your reputation using tools like Google Postmaster Tools, Microsoft SNDS, and third-party reputation monitoring services

Practice Good List Hygiene

List quality directly impacts engagement metrics, bounce rates, and complaint rates—all crucial factors in your sender reputation.

Implement a Sunset Policy

A sunset policy is a systematic approach to handling inactive subscribers—those who haven't opened or clicked your emails for an extended period (typically 3-6 months).

A basic sunset process might look like this:

1. Identify inactive subscribers (no opens/clicks for X months)
2. Send a re-engagement campaign series (2-3 emails with compelling content)
3. For those who re-engage, return them to your regular sending
4. For those who remain inactive, either:
   • Reduce sending frequency significantly
   • Stop sending promotional content but maintain transactional emails
   • Remove them from your list entirely (with notification)

Email Content and Design Best Practices

What's inside your emails plays a crucial role in deliverability. Spam filters analyze content to determine if an email should be flagged, and recipients decide whether to engage or mark emails as spam based on what they see.

Create Balanced HTML-to-Text Ratios

Emails with too much HTML and too little text often trigger spam filters. For optimal deliverability:

• Maintain a good balance between text and images
• Avoid sending emails that are one large image
• Always include a plain text version of your HTML emails
• Keep HTML clean and well-structured

Avoid Spam Trigger Words and Patterns

While no single word will automatically send your email to spam, certain words and phrases—especially when used excessively or in combination—can increase spam scores:

• Phrases like "100% free," "guaranteed," "no obligation"
• Excessive use of capital letters and exclamation points
• Currency symbols, especially $ and € when paired with numbers
• High-pressure sales language
• References to common scam topics (medications, get-rich-quick schemes, etc.)

Optimize Links and Media

• Use reputable link shorteners or, better yet, full URLs
• Avoid excessive links (especially to different domains)
• Ensure all linked domains have good reputations
• Host images on reliable, fast servers
• Compress images appropriately for email (under 200KB total)
• Include descriptive ALT text for all images

Create Mobile-Responsive Designs

With over 60% of emails now opened on mobile devices, responsive design isn't just about user experience—it impacts engagement metrics that influence deliverability:

• Use responsive email templates
• Keep designs simple and easily scannable on small screens
• Ensure text is readable without zooming
• Make CTAs touch-friendly (minimum 44x44 pixels)
• Test emails across multiple devices and email clients

Engagement Optimization

Email providers increasingly use recipient engagement as a key factor in determining inbox placement. Emails that generate positive engagement are more likely to reach the inbox for all subscribers.

Improve Open Rates

While Apple's Mail Privacy Protection has changed how open rates are measured for some users, opens still matter for deliverability with many providers.

• Craft compelling, honest subject lines (30-50 characters ideal)
• Personalize subject lines when relevant
• Test different send times to find optimal engagement windows
• Use recognizable sender names (person@brand.com or "Name from Brand")
• Optimize preheader text to complement your subject line

Encourage Clicks and Replies

Clicks and replies are strong engagement signals that positively impact deliverability:

• Include clear, compelling calls-to-action
• Ask questions that encourage replies
• Request feedback or reviews
• Make content relevant and valuable to recipients
• Segment your audience to increase relevance

Segment and Personalize

Targeted, relevant emails generate more positive engagement and fewer spam complaints:

• Segment by past purchase behavior
• Segment by engagement level (high, medium, low)
• Segment by interests or preferences
• Personalize content based on demographic data
• Tailor frequency based on individual subscriber preferences

Compliance and Best Practices

Following email regulations isn't just about avoiding legal issues—it also improves deliverability by aligning your practices with what mailbox providers expect from legitimate senders.

Comply with Email Regulations

Major email regulations include:

• CAN-SPAM Act (US): Requires commercial emails to include unsubscribe options and physical address, prohibits deceptive subject lines and headers
• GDPR (EU): Requires explicit consent, data protection measures, and the right to erasure
• CASL (Canada): Requires explicit or implied consent and easy unsubscribe options
• CCPA/CPRA (California): Gives consumers rights regarding their personal information

Key compliance practices include:

• Obtain and maintain proper consent records
• Include clear unsubscribe mechanisms in every marketing email
• Honor unsubscribe requests promptly (within 10 business days, but ideally immediately)
• Include your physical address in all marketing emails
• Use accurate, non-deceptive subject lines and "From" names
• Maintain a clear privacy policy that covers email marketing practices

Monitor and Adapt

Email deliverability isn't a "set it and forget it" task. Continuous monitoring and improvement are essential:

• Set up DMARC reporting to monitor authentication
• Use seed list testing to check inbox placement across providers
• Monitor bounce codes and feedback loops
• Track engagement metrics over time
• Stay informed about changes to mailbox provider algorithms
• Test and measure the impact of changes to your email program

Conclusion: A Holistic Approach to Deliverability

Email deliverability requires a holistic approach that encompasses technical configuration, content quality, list management, and recipient engagement. By implementing the best practices outlined in this guide, you can significantly improve your inbox placement rates and get more value from your email communications.

Remember that deliverability isn't just about following rules—it's about creating valuable, engaging experiences for your recipients. When you consistently deliver content that subscribers want to receive, engagement improves naturally, and deliverability follows.

Finally, the email landscape continues to evolve, with new technologies, regulations, and filtering approaches emerging regularly. Stay informed, test consistently, and be prepared to adapt your strategy as best practices evolve.

Ready to test your email delivery setup? Our SMTP Email Tester can help you identify technical issues that might be impacting your deliverability.