Email deliverability is essentially the ability of your emails to reach the recipient's inbox rather than ending up in spam folders or being blocked entirely. It's a critical aspect of any email marketing or communication strategy, directly impacting whether your messages are seen and acted upon.
Achieving high deliverability requires a multi-faceted approach, blending technical configurations with strategic content and list management practices. It's not just about hitting send, but ensuring your emails are welcomed by mailbox providers and recipients alike.
If you're facing challenges with your emails not reaching the inbox, or noticing declining open rates, it's time to dive into the core components of email deliverability and implement proven strategies for improvement.
Establishing a strong sender identity
A strong technical foundation is paramount for email deliverability. This involves correctly configuring email authentication protocols, which prove your emails are legitimate and prevent spoofing. Without these, mailbox providers are far more likely to flag your messages as suspicious or outright block them.
The primary protocols are SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance). SPF allows you to specify which mail servers are authorized to send email on behalf of your domain. DKIM adds a digital signature to your emails, verifying that the message has not been tampered with in transit. DMARC builds on SPF and DKIM, allowing you to tell receiving mail servers what to do with emails that fail authentication, and provides valuable reporting. Implementing all three is crucial for establishing sender trust, as highlighted in this guide on email deliverability best practices.
The importance of DMARC policies
As of early 2024, major mailbox providers like Gmail and Yahoo have made DMARC policies mandatory for bulk senders. Failing to implement DMARC, or having a misconfigured SPF or DKIM record, can severely impact your deliverability. Ensure your records are accurate and monitored regularly. If you need help with DMARC, we have a simple guide to DMARC, SPF, and DKIM.
Example SPF recordDNS
v=spf1 include:_spf.example.com ~all
Another crucial technical aspect is your IP and domain reputation. When you start sending emails from a new IP address or domain, it has no prior reputation. Mailbox providers are wary of new senders to prevent spam. This is where IP warming comes in. It's the process of gradually increasing the volume of email sent from a new IP address or domain over several days or weeks. This establishes a positive sending history and builds trust with mailbox providers, showing them you are a legitimate sender.
Whether you use a dedicated IP or a shared IP can also impact your deliverability. A dedicated IP gives you full control over your sending reputation, as it's not influenced by other senders. However, it requires consistent high volume sending to maintain a good reputation. Shared IPs are often used by smaller senders, where your reputation is pooled with other users. While convenient, a poor sender on a shared IP can negatively affect your deliverability, making improving your email reputation vital.
Crafting valuable content and fostering engagement
Beyond technical setup, the content of your emails and how recipients engage with them significantly influence deliverability. Mailbox providers prioritize delivering emails that users want to receive and engage with. This means your content needs to be relevant, valuable, and free of spam triggers.
Common content pitfalls
Generic content: Sending the same email to everyone on your list, regardless of their interests or past interactions.
Spammy language: Using excessive capitalization, exclamation marks, or suspicious phrases.
Large email sizes: Emails with heavy images, excessive HTML, or attachments that can exceed provider limits.
Poor accessibility: Relying heavily on images for text content, which can be flagged by filters or inaccessible to some users.
Link shorteners: Using generic or untrusted URL shorteners, which are often associated with spam.
Best practices for content
Audience segmentation: Divide your list into smaller groups based on demographics, interests, or engagement levels.
Personalization: Tailor subject lines, content, and offers to individual subscribers.
Concise design: Aim for a healthy text-to-image ratio and optimize images to reduce file size. For more details, consult this HubSpot guide on email deliverability.
Accessible content: Ensure your emails are readable with images turned off and include alt text for all visuals.
Reputable links: Use your own branded links or those from trusted providers, avoiding public shorteners.
Beyond the content itself, recipient engagement metrics, such as open rates, click-through rates, and reply rates, are closely monitored by mailbox providers. High engagement signals that your emails are valued, boosting your sender reputation. Conversely, low engagement, or worse, high complaint rates, can signal to providers that your emails are unwanted, leading to stricter filtering or even blocklisting.
Maintain a consistent sending frequency, avoiding sudden spikes or drops in volume. Sporadic sending patterns can trigger spam filters. Also, consider the best time to send emails to your audience to maximize opens and clicks, further enhancing your engagement metrics.
Maintaining a healthy and engaged audience
The foundation of good email deliverability is a clean, healthy, and engaged email list. Sending emails to inactive, invalid, or uninterested addresses can severely damage your sender reputation and lead to higher bounce rates and spam complaints. This is why strict list hygiene practices are non-negotiable.
Always prioritize obtaining explicit consent from recipients. Implement a double opt-in process where subscribers confirm their subscription after signing up. This verifies their email address, ensures they genuinely want your emails, and significantly reduces the likelihood of spam complaints and hard bounces. Double opt-in builds a higher quality, more engaged list from the start.
Benefits of list segmentation and hygiene
Reduced complaints: Sending only to engaged users minimizes reports.
Regularly clean your email list by removing unengaged subscribers and bounced addresses. Hard bounces (permanent delivery failures) and spam complaints are major red flags to mailbox providers and can quickly land your domain on a blocklist (or blacklist). Implement a clear and easy-to-find unsubscribe option in every email, and honor unsubscribe requests promptly. Making it easy to opt-out reduces the chances of recipients marking your emails as spam.
Engagement level
Sending frequency
Highly engaged (recent opens/clicks)
Frequent emails, personalized offers.
Moderately engaged (some recent interaction)
Regular cadence, focused content.
Low engagement (no interaction in months)
Reduced frequency, re-engagement campaigns, or removal.
Even with best practices in place, email deliverability is an ongoing process that requires continuous monitoring and adaptation. Key metrics like open rates, click-through rates, bounce rates, and spam complaint rates provide critical insights into your sending health. Regularly review these metrics to identify trends and potential issues. You can also run an email deliverability test to see where your emails land.
Beware of misleading deliverability scores
Many online tools offer deliverability 'scores' or 'tests' that claim to predict inbox placement. However, many of these use outdated spam filtering techniques (like SpamAssassin, which is over 20 years old) that are not used by major mailbox providers. Relying on such tools can give a false sense of security or urgency. True deliverability success comes from consistent adherence to best practices, not from a score on a generic checker.
Google Postmaster Tools is an invaluable free resource for senders. It provides detailed data on your domain's reputation, spam rate, IP reputation, and DMARC failures, specifically for emails sent to Gmail users. Regularly checking these reports can help you identify deliverability issues early and take corrective action. This tool is essential for maintaining a healthy sender reputation, as explained in our ultimate guide to Google Postmaster Tools.
Monitoring various blocklists (also known as blacklists) is also a good practice. While major mailbox providers use their own internal algorithms, being listed on a public blocklist can still impact your deliverability, especially with smaller or corporate email servers. Regularly check if your IP or domain has been listed and take immediate steps for delisting if necessary. You can also learn more about email blocklists in our in-depth guide.
Views from the trenches
Best practices
Always use a double opt-in process for new subscribers to ensure high-quality, engaged lists.
Segment your email lists based on engagement and interests to send more relevant content, increasing opens and clicks.
Ensure your email authentication records (SPF, DKIM, DMARC) are correctly configured and monitored.
Common pitfalls
Relying on outdated online spam checkers that use SpamAssassin, which don't reflect current mailbox provider filtering.
Ignoring email size warnings, as very large emails (e.g., over 100KB) can sometimes be filtered by certain spam filters.
Linking to untrusted third-party domains or generic link shorteners in your emails.
Expert tips
Focus on the actual sending practices, as deliverability is a result of your habits, not just a score from a tool.
Prioritize email accessibility, ensuring your messages are readable even with images turned off.
Understand that even excellent senders can occasionally encounter spam folder placement, so continuous vigilance is key.
Expert view
Expert from Email Geeks says that while some older or custom spam filters might flag messages exceeding 100kb, major mailbox providers do not typically filter emails into spam based solely on size. The primary effect of exceeding this size is usually just content truncation, where the recipient sees a 'Show complete mail' link.
May 17, 2022 - Email Geeks
Expert view
Expert from Email Geeks says that many online email checking services provide unhelpful or misleading information because they often use outdated filtering systems like SpamAssassin, which are no longer employed by mainstream mailbox providers. Senders should be cautious of such tools as they can create a false sense of security or undue alarm.
May 17, 2022 - Email Geeks
Your path to better email delivery
Improving email deliverability is a continuous effort that involves a holistic approach to your email program. It's about building and maintaining trust with mailbox providers and your subscribers.
By focusing on robust technical authentication, crafting engaging and relevant content, meticulously managing your subscriber list, and diligently monitoring your performance, you can significantly enhance your inbox placement rates and ensure your messages consistently reach their intended audience. Remember, deliverability is a journey, not a destination.
Gmail and 
Yahoo have made DMARC policies mandatory for bulk senders. Failing to implement DMARC, or having a misconfigured SPF or DKIM record, can severely impact your deliverability. Ensure your records are accurate and monitored regularly. If you need help with DMARC, we have a simple guide to DMARC, SPF, and DKIM.
Remove from list to prevent deliverability issues, especially for 
