How can I improve my email open rates and avoid spam filters?
Michael Ko
Co-founder & CEO, Suped
Published 3 May 2025
Updated 16 Aug 2025
6 min read
Achieving high email open rates and successfully navigating spam filters are fundamental goals for any sender. It's not just about reaching the inbox, but also about engaging your audience once you get there. A low open rate often indicates that your emails are either not making it to the primary inbox or they aren't compelling enough to be opened.
The landscape of email deliverability is constantly evolving, with new sender requirements from major mailbox providers like Google and Yahoo shaping best practices. Understanding these nuances is crucial to ensure your messages bypass the dreaded spam folder and land where they belong: in the recipient's main inbox.
Establish strong sender reputation
Your sender reputation is the cornerstone of email deliverability. Mailbox providers assess your domain and IP reputation to determine whether your emails are legitimate or potential spam. This assessment relies heavily on proper email authentication protocols.
Implementing SPF, DKIM, and DMARC is non-negotiable for improving deliverability and protecting your domain from spoofing. SPF (Sender Policy Framework) specifies which mail servers are authorized to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a digital signature to your emails, verifying that the message has not been altered in transit. DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF and DKIM, telling receiving servers how to handle emails that fail authentication and provides reports on your email traffic. Ignoring these can significantly hurt your chances of reaching the inbox, leading to lower open rates and higher spam placement.
A robust email authentication setup signals to mailbox providers that you are a legitimate sender, which is vital for building a positive sender reputation. If your emails consistently fail authentication checks, they are more likely to be sent to the spam folder or rejected outright, regardless of your content or list quality.
This DMARC record tells receiving servers to quarantine emails that fail authentication. The rua and ruf tags specify where aggregate and forensic reports should be sent, which are invaluable for monitoring your domain's email health.
Craft compelling emails and manage expectations
Even with perfect authentication, your emails still need to capture attention and provide value to be opened. The subject line and preview text are your first and best opportunities to engage recipients.
Crafting clear, concise, and compelling subject lines is key. Avoid generic phrases, spammy keywords (like FREE!!! or Buy now), excessive capitalization, or exclamation marks, as these can trigger spam filters and lead to a low open rate. Personalization, where appropriate, can also make a significant difference. Furthermore, ensure your content is relevant to the recipient's interests and expectations set during signup. If you send 40+ emails in a month to a subscriber, each one must be highly relevant and anticipated, or you risk disengagement and spam complaints.
The frequency of your emails also plays a role. Sending too many emails, even if relevant, can lead to unsubscribe requests or recipients marking your messages as spam. Conversely, sending too infrequently might cause your audience to forget they subscribed. Finding the right balance often involves A/B testing and monitoring subscriber engagement. Consider reducing high sending frequencies, especially for recipients who haven't opened or clicked in several months.
Effective subject lines
Use clear, concise, and benefit-oriented language. Personalize where possible. Create curiosity without being misleading.
Example: "Your weekly update: new features and tips"
Personalization: "[Name], your exclusive offer awaits"
Subject lines to avoid
Avoid all caps, excessive punctuation, and spam trigger words. Do not use deceptive or clickbait phrases that don't match content.
Example: "FREE MONEY NOW!!! ACT FAST!"
Deceptive: "Re: Your recent order" (when it's a marketing email)
Maintain a healthy email list
A clean and engaged email list is paramount for improving open rates and avoiding spam filters (or blocklists). Sending to outdated, invalid, or unengaged email addresses can severely damage your sender reputation and lead to higher bounce rates and spam complaints.
Regularly cleaning your email list is essential. Remove inactive subscribers who haven't opened or clicked your emails in a long time. These contacts can become spam traps, which are email addresses specifically set up by internet service providers (ISPs) and blacklist (or blocklist) operators to identify senders of unsolicited bulk email. Hitting spam traps will lead to your IP or domain being added to a blocklist.
Implementing a double opt-in process for new subscribers can prevent invalid addresses from entering your list and ensure that only genuinely interested individuals receive your emails. This proactive step can significantly reduce future deliverability issues and improve the overall quality of your engagement metrics.
Email list best practices
Segment your audience: Send targeted content to specific groups based on their interests or behavior. This dramatically increases relevance and engagement. This is one of the best ways to avoid spam filters.
Re-engagement campaigns: Attempt to re-engage inactive subscribers with special offers or content before removing them.
Monitor unsubs/complaints: High rates indicate issues with content, frequency, or list quality. Address these promptly.
Monitor performance and adapt
Email deliverability isn't a set-it-and-forget-it task. Continuous monitoring and adaptation are crucial for sustained success. Regularly check your sender reputation using tools like Google Postmaster Tools. These provide valuable insights into your domain and IP reputation, spam rates, and delivery errors.
While open rates can offer a general indication of engagement, understand that their accuracy has been impacted by privacy features like Apple Mail Privacy Protection, which pre-fetches emails. This can artificially inflate reported open rates. Focus more on click-through rates, conversions, and direct feedback from subscribers to gauge true engagement and value. If your open rate is consistently low, like 11%, it often suggests that your emails are not reaching the inbox, making it a deliverability issue.
A/B testing different subject lines, send times, and content formats can help you optimize your campaigns for better engagement. Pay attention to how different segments of your audience respond. By continually analyzing your metrics and adjusting your strategy, you can proactively address issues and improve your email deliverability and open rates over time.
Views from the trenches
Best practices
Send frequency should match subscriber expectations; if they opted in for daily, deliver daily.
Relevant content is key: email should always align with subscriber interests and expectations.
Leverage double opt-in to ensure a high-quality, engaged subscriber list from the start.
Segment your email list to send highly targeted messages that resonate with specific groups.
Common pitfalls
Sending emails too frequently without new, compelling content can quickly lead to unsubscribes.
Ignoring email authentication (SPF, DKIM, DMARC) is a common mistake that hurts deliverability.
Not cleaning inactive subscribers from your list can increase spam trap hits and damage reputation.
Relying solely on open rates as a metric can be misleading due to pre-fetching by email clients.
Expert tips
Regularly monitor your domain reputation and spam placement using postmaster tools.
A/B test subject lines, send times, and content to optimize engagement for your specific audience.
Focus on subscriber value: if your email's goal aligns with the subscriber's goal, it will perform better.
Consider engaging users on platforms like
Marketer view
Marketer from Email Geeks says that high sending frequencies are acceptable only if each message promotes something new and recipients are interested in that volume of email. It is advisable to exclude recipients who haven't opened or clicked in several months.
2023-04-13 - Email Geeks
Marketer view
Marketer from Email Geeks says that open rates increase when sending relevant content that people want or expect, and spam votes increase if this advice is not followed. The 11% open rate is also mostly meaningless due to pre-fetching.
2023-04-13 - Email Geeks
Summary of key strategies
Improving email open rates and avoiding spam filters is a multifaceted effort that goes beyond just writing good subject lines. It demands a holistic approach, starting with solid technical foundations.
By prioritizing technical configurations, maintaining a healthy email list, crafting engaging and relevant content, and continuously monitoring your performance, you can significantly enhance your email program's effectiveness. These strategies will help ensure your messages consistently reach the inbox and captivate your audience.
