What is a good deliverability guide for email marketers?
Matthew Whittaker
Co-founder & CTO, Suped
Published 2 Jun 2025
Updated 17 Aug 2025
11 min read
For email marketers, getting your messages into the inbox, rather than the spam or junk folder, is the ultimate goal. This isn't just about sending emails, it's about email deliverability. A strong deliverability rate ensures your campaigns reach their intended audience, fostering engagement and driving results. Without it, even the most compelling email content falls flat, lost in the digital void.
Achieving good email deliverability is a complex dance between technical configurations, sender reputation, list hygiene, and content quality. It's a continuous process that requires vigilance and adherence to best practices, as mailbox providers like Google and Outlook constantly update their filtering algorithms. A good guide demystifies this process, offering clear, actionable steps for marketers at any stage of their journey.
Understanding sender reputation
At the core of email deliverability lies sender reputation, which is essentially how trustworthy mailbox providers view your sending domain and IP address. A good reputation means your emails are more likely to bypass spam filters and reach the inbox. Conversely, a poor reputation can lead to emails being blocked or routed directly to the junk folder. Factors influencing this include your sending history, complaint rates, bounce rates, and whether your IP or domain appears on any blocklists (or blacklists).
Building a solid reputation starts with consistent sending practices and maintaining clean subscriber lists. It’s also crucial to implement email authentication protocols such as SPF, DKIM, and DMARC. These technical records verify your emails, proving that they originate from your legitimate domain and haven't been tampered with. Proper configuration of these protocols is fundamental for showing mailbox providers you are a legitimate sender.
Monitoring your sender reputation regularly, perhaps through Google Postmaster Tools, allows you to catch potential issues early. This proactive approach can prevent minor hiccups from escalating into major deliverability crises. An email deliverability guide should emphasize this continuous monitoring and the importance of understanding the various metrics that contribute to your sender score.
Lastly, for a comprehensive overview of how email deliverability operates in today's marketing environment, it's beneficial to explore resources that explain how email deliverability works.
List hygiene and engagement
The quality of your email list profoundly impacts your deliverability. Sending to an unengaged, outdated, or poorly sourced list is a surefire way to damage your sender reputation. A good deliverability guide will always highlight the critical role of list hygiene and permission-based marketing. This means obtaining explicit consent from subscribers, ideally through a double opt-in process, ensuring that only genuinely interested recipients receive your emails.
Regularly cleaning your email list is not just a suggestion, it's a necessity. Removing inactive subscribers, hard bounces, and addressing soft bounces helps maintain a healthy list. Unengaged recipients are less likely to open or click your emails, which negatively signals to mailbox providers that your content isn't relevant, potentially leading to lower inbox placement rates. Tools that help you identify and remove these problematic addresses are invaluable.
Beware of spam traps, which are email addresses specifically set up by mailbox providers and blocklist (or blacklist) operators to identify senders with poor list management practices. Hitting a spam trap can severely harm your sender reputation and lead to immediate blacklisting. Understanding how spam traps work is key to avoiding them.
Spam trap warning
Sending to spam traps is one of the quickest ways to get your domain or IP address listed on a blocklist. Always ensure your list acquisition methods are legitimate and that you regularly scrub unengaged or old contacts to minimize this risk. Even a few spam trap hits can significantly impact your deliverability across all mailbox providers.
Finally, integrating proper list segmentation and engagement strategies is vital. Segmenting your audience allows for more targeted and personalized content, which naturally leads to higher engagement rates and improved deliverability. A good guide will explain how to leverage these strategies effectively to keep your list clean and active.
Content quality and engagement
Even with a stellar sender reputation and a pristine list, your emails can still miss the inbox if your content triggers spam filters. Mailbox providers analyze various aspects of your email content, including subject lines, body text, image-to-text ratio, and link quality. Overly promotional language, excessive use of all caps or exclamation marks, and suspicious links can all raise red flags. Your content must be relevant and valuable to your subscribers.
Engagement signals are increasingly important. Mailbox providers observe how recipients interact with your emails: do they open them, click links, reply, forward, or move them to the junk folder? Positive interactions boost your sender reputation, while negative ones can hurt it. This means your content needs to be compelling enough to encourage opens and clicks, while avoiding anything that might lead to complaints or unsubscribes.
Personalization goes a long way in improving engagement. Generic, one-size-fits-all emails are often ignored. Tailoring content based on subscriber preferences, past behavior, or demographic data makes your emails more relevant and valuable, increasing the likelihood of positive interactions. A good guide will provide strategies for effective personalization that resonates with your audience.
Good content practices
Clear subject lines: Concise and accurately reflect content.
Relevant content: Provides value and meets subscriber expectations.
Balanced media: Good text-to-image ratio and minimal suspicious links.
Engagement focus: Encourages opens, clicks, and replies.
Bad content practices
Spam trigger words: Overuse of words like 'free', 'win', 'guarantee'.
Excessive capitalization: All caps in subject lines or body.
Image-heavy emails: Little text, mostly images, which can look suspicious.
Broken links or suspicious URLs: Can lead to blocklisting.
Testing your email content before sending is a valuable step. This includes checking for broken links, rendering issues across different email clients, and assessing your spam score. By proactively identifying and fixing potential content issues, you can significantly improve your chances of landing in the inbox. You can find out more about email deliverability best practices to improve inbox placement.
Technical setup and monitoring
Beyond content and list hygiene, mastering the technical aspects of email sending is non-negotiable for marketers. This primarily revolves around robust email authentication, which verifies your identity as a sender. SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) work together to protect your domain from spoofing and phishing, while simultaneously signaling legitimacy to mailbox providers. Setting these up correctly is a fundamental step for strong deliverability, and a good guide should offer clear instructions, perhaps explaining DMARC, SPF, and DKIM in simple terms.
DMARC, in particular, allows you to tell mailbox providers how to handle emails that fail SPF or DKIM authentication. By implementing a DMARC policy, you gain visibility into your email sending ecosystem through DMARC reports, which detail authentication results and potential misuse of your domain. Gradually transitioning your DMARC policy to quarantine or reject helps enforce stricter authentication and further improve deliverability.
Another crucial technical consideration is IP warming, especially if you're sending from a new IP address or significantly increasing your sending volume. Mailbox providers are wary of sudden spikes in email volume from unknown or low-reputation IPs, often flagging such emails as spam. IP warming involves gradually increasing your sending volume over time, allowing mailbox providers to build a positive reputation for your IP. This methodical approach is vital for long-term deliverability success.
Finally, understanding and monitoring email blocklists (or blacklists) is essential. If your IP or domain gets listed, your emails can be outright blocked by receiving servers. A good guide will explain what happens when your email is blacklisted and how to proactively check for listings and request delisting if necessary. This holistic approach to technical setup and ongoing monitoring forms the bedrock of a successful email marketing program.
Analytics and troubleshooting
To truly gauge your deliverability, you need to understand the data. This involves not just tracking open and click rates, but delving deeper into metrics like bounce rates (hard and soft), complaint rates, and unsubscribe rates. These metrics provide insights into your list health and content quality, helping you identify areas for improvement. A good guide for marketers will detail how to analyze these metrics and what benchmarks to aim for, generally recommending a deliverability rate above 95%.
Beyond standard analytics, leveraging tools that provide detailed insights into your inbox placement across various mailbox providers is highly beneficial. These tools can show you if your emails are landing in the primary inbox, promotions tab, or spam folder. This granular data allows for more targeted optimization efforts. Additionally, proactively running email deliverability tests can simulate how your emails are perceived by different filters.
Understanding why your emails might be going to spam is the first step toward fixing the issue. Whether it's due to authentication failures, content problems, or poor sender reputation, diagnostics are crucial. A comprehensive guide will equip marketers with the knowledge to troubleshoot common deliverability problems and implement corrective measures effectively. This empowers you to take control of your email program.
Furthermore, recognizing the hidden factors that affect your deliverability rate can be a game-changer. Sometimes, the issues aren't immediately obvious from basic analytics. These can include complex interactions with recipient mail servers, subtle changes in reputation signals, or even nuances in how email services process certain types of content. Staying informed about these advanced aspects can give you a significant edge in optimizing your email campaigns.
Views from the trenches
Best practices
Maintain a consistent sending volume to help build a reliable sender reputation over time.
Regularly clean your email list by removing inactive subscribers and hard bounces.
Implement a double opt-in process for all new subscribers to ensure explicit consent.
Segment your audience for personalized content, leading to higher engagement rates.
Proactively monitor your sender reputation and blocklist status using available tools.
Common pitfalls
Ignoring high bounce rates, which signal an unhealthy email list and can damage your reputation.
Purchasing email lists, leading to low engagement, high complaints, and spam trap hits.
Sending emails with generic content that lacks personalization and relevance for recipients.
Failing to implement or properly configure email authentication protocols like SPF, DKIM, and DMARC.
Not warming up new IP addresses or domains, causing sudden volume spikes that trigger spam filters.
Expert tips
Utilize DMARC reporting to gain visibility into your email ecosystem and identify potential issues.
Prioritize email engagement metrics, such as opens and clicks, as key indicators of deliverability.
Continuously test your email content, including subject lines and preheaders, to optimize performance.
Regularly review feedback loops from ISPs to understand and address user complaints promptly.
Stay updated on major mailbox provider requirements to adapt your sending practices accordingly.
Expert view
Expert from Email Geeks says a good deliverability guide should cater to marketers from novice to intermediate levels, offering accessible and actionable insights.
March 7, 2024 - Email Geeks
Expert view
Expert from Email Geeks says to carefully review all links in a deliverability guide, especially those pointing to technical portals, ensuring they lead to the correct resources or products.
March 7, 2024 - Email Geeks
The path to consistent inbox delivery
A good deliverability guide for email marketers is more than just a list of tips. It's a foundational resource that explains the interconnected elements of sender reputation, list hygiene, content quality, and technical configuration. It empowers marketers to understand the "why" behind deliverability challenges and provides the "how" to overcome them, ensuring their messages consistently reach the inbox.
The landscape of email marketing is constantly evolving, with mailbox providers regularly updating their algorithms and requirements. Therefore, a truly effective guide will emphasize the importance of continuous learning and adaptation. Staying informed about new authentication standards, changes in filtering practices, and emerging threats like sophisticated spam traps is crucial for long-term success.
Ultimately, the goal is to build and maintain trust with both your subscribers and mailbox providers. By consistently sending valuable, relevant emails from an authenticated domain and meticulously managing your sender reputation, marketers can significantly improve their inbox placement rates and achieve their campaign objectives. This proactive and informed approach is the hallmark of a successful email marketer in today's digital world.
Outlook constantly update their filtering algorithms. A good guide demystifies this process, offering clear, actionable steps for marketers at any stage of their journey.
