How to Improve Email Deliverability: 18 Best Practices That Actually Work

Your emails can't get opened, clicked, or converted if they never reach the inbox in the first place.

Email deliverability is the foundation of every successful email program. It doesn't matter how compelling your subject lines are or how beautiful your templates look if your messages land in spam folders instead of inboxes.

Fortunately, improving email deliverability isn't complicated. You don't need advanced technical skills or a massive budget. You just need to follow proven best practices, maintain good sending habits, and treat your subscribers right.

Below, we'll walk you through strategies to improve your email deliverability and keep your messages landing where they belong.

What Is Email Deliverability?

Email deliverability refers to the ability of your emails to successfully reach recipients' inboxes. It's not just about whether an email gets sent. It's about whether it lands where it's supposed to.

Deliverability is the process of effectively reaching the inboxes of each of your subscribers. Undelivered emails generate zero engagement, zero clicks, and zero conversions, no matter how good the content inside them is.

Here's a breakdown of key components:

• Delivery: When an email is accepted by the recipient's mail server.
• Deliverability: When an email actually reaches the inbox, not the spam or junk folder.
• Delivery rate: The percentage of emails accepted by recipient servers.
• Deliverability rate: The percentage of emails that land in inboxes.

You can have a 99% delivery rate but only 70% deliverability if most of your emails end up in spam folders. The goal is to maximize both.

How Email Delivery Works Behind the Scenes

When you send an email, it goes through several steps before it reaches the recipient:

1. Your email client or sending platform composes the message and hands it to an SMTP server.
2. The SMTP server looks up the recipient's domain through DNS servers to find the correct mail server.
3. The recipient's mail server receives the message and decides where to place it: inbox, spam folder, or reject it entirely.

That decision is based on a combination of factors including your sender reputation, email authentication, content quality, and subscriber engagement history.

Factors That Affect Email Deliverability

Before diving into best practices, it helps to understand the factors that determine whether your emails reach the inbox:

Internet Service Providers (ISPs): ISPs like Gmail, Yahoo, and Outlook use complex algorithms to filter incoming emails. They evaluate your sending history, domain reputation, and subscriber engagement to decide whether your email belongs in the inbox or spam.

Email Service Providers (ESPs): The platform you use to send emails plays a role. Reputable ESPs have established relationships with ISPs and maintain shared or dedicated IP pools with good reputations.

IP address reputation: Your sending IP has a reputation score based on your sending history. High bounce rates, spam complaints, and low engagement can damage this score and reduce deliverability.

Sender and domain reputation: ISPs track the reputation of your sending domain separately from your IP. A domain with a history of spam complaints or high bounce rates will face deliverability challenges regardless of which IP it sends from.

Engagement metrics: ISPs monitor how recipients interact with your emails. Opens, clicks, replies, and forwards are positive signals. Spam complaints, deletes without reading, and lack of engagement are negative signals.

Email content and formatting: The content of your email, including subject lines, body text, images, and links, is scanned by spam filters. Poorly formatted emails, broken links, or content that resembles spam can trigger filtering.

How to Improve Email Deliverability

Improving your email deliverability isn't just about technical fixes. It's about creating a holistic strategy that prioritizes subscriber engagement and sender reputation. Here are proven techniques to prevent failures and improve your email delivery rates for the long term.

1. Authenticate Your Email Domain

Email authentication proves to ISPs that you are who you say you are and that your emails are legitimate. Without proper authentication, you risk falling victim to email spoofing (someone impersonating your domain) and experiencing poor delivery rates.

There are three key authentication protocols to implement:

• SPF (Sender Policy Framework): Specifies which mail servers are authorized to send email on behalf of your domain. Add an SPF record to your DNS settings that lists your authorized sending IPs.
• DKIM (DomainKeys Identified Mail): Adds a digital signature to your outgoing emails. The recipient's server verifies this signature against a public key in your DNS records to confirm the email hasn't been tampered with.
• DMARC (Domain-based Message Authentication, Reporting and Conformance): Builds on SPF and DKIM by telling receiving servers what to do when authentication fails (quarantine, reject, or allow). DMARC also provides reporting so you can monitor authentication results.

Work with your IT team to connect your email sending domain by adding these records to your Domain Name Server. This makes your emails look more authentic to email filters. If your organization uses a DMARC policy, make sure all necessary records are updated when you add new sending services.

2. Maintain Proper IP Allocation

As your email program grows, you need the right infrastructure to support it. There are two options for sending IPs:

Shared IP: Your emails are sent from an IP address shared with other senders. Your deliverability is partially influenced by the sending behavior of everyone on that IP.

Dedicated IP: You get your own IP address. Your deliverability depends entirely on your own sending practices. This gives you full control over your sender reputation.

Once you reach approximately 25,000 daily emails, consider moving to a dedicated IP address. Dedicated IPs are particularly beneficial for high-volume senders or businesses with strict deliverability requirements.

Don't add multiple IPs to try to avoid penalties. ISPs are smarter than that and will block an entire IP pool if they suspect this tactic.

3. Warm Up Your Email Sending

To establish a positive reputation with inbox providers, gradually ramp up the volume and frequency of the emails you send:

• New dedicated IP: When you add a new dedicated IP, go through a warm-up period of 30 to 60 days. Start with a low volume of emails to your most engaged subscribers and gradually increase the volume over time.
• New domain or ESP migration: If you recently migrated to a new domain or email service provider, mailbox providers will not immediately recognize the new domain. Send a low number of emails at first, then gradually increase your volume over the next 30 to 60 days.
• Monitor during warm-up: Regularly check your sending reputation, delivery rates, and engagement rates throughout the warm-up period. Watch for cumulative click and open rates to confirm that ISPs are building trust in your sending.

Warming up builds trust with ISPs incrementally. Sending your full volume from day one on a new IP or domain signals spam behavior.

4. Perfect the Opt-In Process

How you collect email addresses plays a large role in your deliverability rates. An optimized opt-in process ensures that your email list is full of engaged users.

If you are sending email to people who didn't agree to receive messages from you, they will mark your emails as spam. ISPs will then treat your entire sending as potentially unwanted, even for subscribers who actually want your email.

Use double opt-in. Double opt-in involves two verifications: the user submits their email address, then receives a confirmation email with a link to verify their subscription. This extra step helps you avoid fake or misspelled email addresses and ensures that all new contacts in your database are actively engaged. Double opt-in signup also helps validate new contacts and prevent hard bounces from invalid addresses.

5. Write Non-Spammy Subject Lines

Your subject lines determine whether a user opens your email. Although ISP filtering systems have become more sophisticated and certain phrases won't automatically land you in spam, it's still wise to avoid common spam triggers.

Phrases to avoid:

• "Eliminate your debt"
• "Risk-free"
• "FREE!!!"
• "Act now" or "Limited time offer" with excessive punctuation
• ALL CAPS subject lines

There is no absolute list of banned words that will guarantee inbox placement. But when writing subject lines, focus on the genuine value of the message without sounding pushy or salesy. Clear, honest subject lines build trust with both your subscribers and ISP spam filters.

6. Create Good Quality Content

High-quality, relevant content is the best way to keep subscribers engaged and ISPs happy. To improve engagement:

• Test your emails before sending. Use test-in-email-client features to make sure your email renders correctly across devices, especially mobile.
• Use personalization. Add personalization tokens (first name, company name, relevant details) to tailor your messaging to specific contacts.
• Send measured email volumes. Avoid sudden spikes in send volume, which can trigger spam filters.
• Keep content relevant. Send content that matches what subscribers signed up for. Irrelevant content drives unsubscribes and spam complaints.

All of your email content, including imagery and links, will be reviewed by ISPs to determine whether it looks like spam, a phishing attempt, or other malicious email. Watch out for broken links, misspellings, missing email headers, or excluding options to unsubscribe. These mistakes increase the odds that your email is flagged as spam.

7. Provide a Preference Center

Once your recipients have agreed to receive email from you, give them control over their experience. A preference center lets subscribers decide:

• How frequently they want to receive emails (daily, weekly, monthly)
• What types of content they want (product updates, promotions, newsletters)
• Which channels they prefer

Putting recipients in control keeps them happy. This happiness translates to better engagement, which ISPs notice and reward with better inbox placement.

8. Keep the Conversation Going

It is a very positive signal to ISPs when your contacts reply to your emails. For that reason:

• Monitor replies and respond in a timely manner.
• Avoid sending emails from a no-reply address that cannot receive responses.
• Encourage two-way communication where appropriate (ask questions, request feedback).

Replies tell ISPs that your subscribers are actively engaged with your emails, which strengthens your sender reputation.

9. Segment Your Email Lists

Segmentation allows you to send relevant content to specific groups within your audience. Tailoring your communications to the interests and behaviors of different segments helps improve engagement rates, which positively impacts your deliverability.

Segmented lists often see:

• Higher open rates
• Higher click-through rates
• Lower unsubscribe rates
• Fewer spam complaints

All of these contribute to a better sender reputation. Segment by purchase history, engagement level, signup source, geographic location, or any other data points relevant to your business.

10. Clean Up Your List Regularly

Don't let your ego get in the way of your email deliverability. A smaller, engaged list is far more valuable than a large list of unresponsive subscribers. The longer you keep inactive and unengaged users on your email list, the more you risk damage to your reputation and deliverability rates.

List hygiene best practices:

• Remove hard bounces immediately. Hard bounced addresses will never work again. Keeping them on your list signals poor audience management to ISPs.
• Provide a clear unsubscribe option. A visible, easy-to-use unsubscribe link in every email automates list cleanup and complies with anti-spam laws (CAN-SPAM, GDPR, CCPA).
• Scrub your list regularly. Remove inactive subscribers, unknown users, and contacts who haven't given you explicit permission to email them.
• Use graymail suppression. Graymail is email that sits unopened in your recipients' inbox. Automatically excluding contacts that aren't engaging with your emails instantly improves your deliverability results.

11. Avoid Spam Traps

Spam traps are email addresses set in place by ISPs and email community organizations to catch spammers sending unwanted email. If you send to a spam trap, you are immediately flagged and put on a deny list.

It is extremely challenging to get yourself off a deny list, so it's best to never end up on one. Even just one spam trap in your list can damage your sender reputation if you unknowingly email it.

How to avoid spam traps:

• Keep a clean list of engaged users
• Never purchase an email list of any sort
• Use double opt-in to validate new subscribers
• Regularly remove inactive addresses that could have been converted to spam traps

12. Avoid Hard Bounces

Hard bounces occur when you send an email to an address that doesn't exist. ISPs factor hard bounces into sender reputation because they signal poor audience management.

Soft bounces, on the other hand, happen when an email address has a temporary issue, like a full inbox. If you're experiencing a lot of bounces, you may need to change how you grow your audience.

To reduce hard bounces:

• Use double opt-in to validate new contacts
• Verify email addresses at the point of collection
• Run your list through an email verification service before large campaigns
• Remove hard bounced addresses from your list immediately

13. Monitor and Manage Your Sender Score

Your sender score is a metric ISPs use to determine whether to deliver your emails to the inbox or spam folder. Think of it as a credit score for your email sending.

Regularly check your sender score using available monitoring tools and take steps to improve it if necessary. This may include:

• Cleaning your email list
• Improving engagement rates
• Following best practices for email content and frequency
• Resolving authentication issues

A consistently good sender score keeps your emails in the inbox across all major mailbox providers.

14. Monitor Your Email Metrics

Keep a close eye on your email performance metrics to maintain and improve your deliverability. Regular monitoring helps you spot potential problems before they become critical.

Key metrics to track:

• Bounce rate: High bounce rates harm your sender reputation. Track both hard and soft bounces.
• Spam complaint rate: If this rises, it's a red flag that your content or sending practices need adjustment.
• Open rates and click-through rates: These engagement signals influence how ISPs view your emails. Low open rates might indicate issues with subject lines or sender name.
• Inbox placement rate: The percentage of your emails actually reaching the inbox.
• Unsubscribe rate: A rising unsubscribe rate signals content or frequency problems.

Use data-driven insights to refine your email marketing approach. By varying your email's send time, subject line, or content, you can run A/B tests to systematically improve these metrics. Small improvements compound over time to significantly boost your overall deliverability.

15. Implement a Sunset Policy

A sunset policy is a strategic approach to managing inactive subscribers. ISPs view consistent sending to inactive addresses as a red flag, which can harm your reputation.

How to implement a sunset policy:

1. Define inactivity: Determine what constitutes an inactive subscriber for your business (e.g., no opens or clicks in 6 months).
2. Create a re-engagement campaign: Before removing inactive subscribers, try to win them back with a targeted campaign offering a reason to re-engage.
3. Set up an automated process: Use email automation to tag and manage inactive subscribers over time.
4. Remove with care: If re-engagement fails, remove inactive subscribers from your main list. Consider keeping them in a separate suppression list.

By focusing on active subscribers, your overall engagement metrics will improve, which in turn improves your deliverability.

16. Perform Deliverability Tests

Before sending out large campaigns, conduct deliverability tests to identify potential issues. These tests help you spot problems with your email content, formatting, or sender authentication that might trigger spam filters.

A deliverability test typically involves sending a sample of your email to test addresses across different email providers. These tests check for:

• Inbox placement: Does your email land in the primary inbox, promotions tab, or spam folder?
• Rendering: How does your email look across different email clients and devices?
• Authentication: Are your SPF, DKIM, and DMARC records set up correctly?
• Content analysis: Does your email content contain elements that might trigger spam filters?
• Link checking: Are all the links in your email working and not blacklisted?

Regularly performing these tests before campaigns helps you catch and fix deliverability issues early.

17. Send Email That People Love

You have to please two parties when trying to improve your email deliverability: the ISPs and your recipients. But if you please the latter, the former will already be taken care of.

ISPs protect the end-user. If your recipients indicate they are happy by opening, clicking, replying, and forwarding, ISPs will keep placing your email in the inbox.

Above all, if your recipients enjoy and derive value from your email, they will interact with your messages. That engagement is the strongest deliverability signal you can send.

18. Stay Updated with Email Deliverability Best Practices

ISPs and email clients frequently update their algorithms and policies. Staying informed is essential to maintaining high deliverability rates.

• Follow industry resources. Read blogs and newsletters from email marketing platforms and deliverability experts for timely updates on industry changes.
• Monitor ISP postmaster pages. Major ISPs like Gmail, Yahoo, and Microsoft publish guidelines and updates on their spam filtering practices.
• Stay informed about legal changes. Business email communications are subject to regulations such as CAN-SPAM, GDPR, and CCPA. Keep track of any changes to these laws that might affect your email practices.
• Review ESP updates. Your email service provider may release new features, compliance requirements, or deliverability tools that can help your program.

Real-World Examples of Businesses That Improved Email Deliverability

Glassdoor: Achieving Stellar Delivery Rates

Glassdoor, the job search and company review platform, faced the challenge of scaling its email program while maintaining high deliverability.

Challenge: Maintaining high deliverability rates while sending millions of emails daily across multiple IPs and domains.

Solution: Implemented a dedicated Email API, leveraged dedicated IP addresses, and partnered with deliverability experts for strategic guidance.

Results:

• 99.5% average monthly delivery rate
• 0.007% average monthly spam rate
• 30% unique email open rates for high-volume emails

Shopify: Empowering Merchants with Reliable Email Delivery

Shopify needed to provide its 1.7 million merchants with reliable email tools for both transactional and marketing communications.

Challenge: Scaling email infrastructure to support both transactional notifications and email marketing for a vast number of merchants.

Solution: Implemented DKIM signing, leveraged IP pool management, and used automated retries in response to mailbox error codes.

Results:

• 99.5% overall delivered rate
• 91.3% inbox placement rate
• Less than 4 seconds p90 average delivery time on all transactional emails

Klaviyo: Driving Engagement Through Reliable Delivery

Klaviyo, a marketing platform for online businesses, needed a scalable email solution to support its growing customer base.

Challenge: Finding a reliable, scalable email delivery solution that would allow the team to focus on building customer experiences.

Solution: Built their email platform on a robust Email API infrastructure, leveraging delivery expertise and infrastructure at scale.

Results:

• 99.94% average delivery rate
• 46.94% open rates for automated welcome series emails
• Ability to send around 10 billion emails per month
• Median delivery speed of 1.9 seconds

Frequently Asked Questions

What is a good email deliverability rate?

A good deliverability rate is 95% or higher. This means at least 95% of your emails are landing in inboxes, not spam folders. If you're consistently below 90%, you have serious deliverability issues that need attention.

How long does it take to improve email deliverability?

It depends on your starting point. If you're fixing basic authentication issues, you might see improvements within a few weeks. If you're recovering from a damaged sender reputation, it could take several months of consistent good sending practices to rebuild trust with ISPs.

What's the difference between delivery rate and deliverability rate?

Delivery rate measures the percentage of emails accepted by recipient servers. Deliverability rate measures the percentage that land in inboxes. You can have a 99% delivery rate but only 70% deliverability if most of your emails end up in spam folders.

Can I fix poor deliverability by switching email service providers?

Not usually. Your sender reputation follows your domain and IP addresses, not your ESP. Switching providers without fixing underlying issues like list quality, engagement rates, and authentication won't solve the problem. Focus on best practices first.

How often should I clean my email list?

Remove hard bounces immediately. For inactive subscribers, run a re-engagement campaign every 6 to 12 months, then remove anyone who doesn't respond. Regular list maintenance keeps your engagement metrics healthy and protects your sender reputation.

Start with a Clean Email List Using BounceCheck

Every deliverability strategy starts with a clean email list. If your list is full of invalid addresses, spam traps, and inactive accounts, no amount of content optimization or authentication will save your inbox placement rate.

BounceCheck helps you eliminate bad addresses before they damage your sender reputation. Every email passes through a 30-step diagnostic pipeline covering syntax validation, domain and MX verification, stealth SMTP handshake, catch-all detection, disposable email detection, role-based account detection, and spam trap identification. Each address receives a 0-100 confidence score, giving you full control to set your own risk thresholds per campaign.

The stealth SMTP engine verifies mailboxes without notifying the recipient or exposing your sending domain. The REST API ships with webhook callbacks and SDKs for Python, Node.js, Ruby, Go, PHP, and cURL, making it easy to plug verification into signup forms, CRM workflows, or pre-campaign list cleaning.

Security includes TLS 1.3 + AES-256 encryption, GDPR and CCPA compliance, and a no-data-selling policy. Credits never expire, and a 14-day money-back guarantee covers unused purchases.

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