What are the best platforms for deliverability testing with Klaviyo?
Michael Ko
Co-founder & CEO, Suped
Published 9 Jul 2025
Updated 17 Aug 2025
8 min read
As a Klaviyo user, you know the power of email marketing for e-commerce. You build beautiful campaigns, segment your audience meticulously, and craft compelling messages. But what happens after you hit Send? The success of your entire email marketing strategy hinges on one critical factor: email deliverability. If your emails aren't reaching the inbox, all that effort is wasted.
Klaviyo is a robust platform, and it offers some basic testing features, such as A/B testing for campaigns and flows. These are valuable for optimizing content, subject lines, and send times. You can also send test emails to your own inbox to preview how a campaign looks and functions. However, these internal tools don't provide a comprehensive view of how your emails will perform across the entire email ecosystem.
To truly ensure your messages land in the inbox and avoid spam folders, you need to look beyond Klaviyo's native capabilities. This means integrating specialized deliverability testing platforms that can simulate real-world inbox placement, check for blocklist (or blacklist) issues, and diagnose underlying technical problems. Choosing the right external tool can significantly impact your campaign performance and overall sender reputation.
Maximizing Klaviyo's internal capabilities
Klaviyo provides helpful built-in features that assist with preliminary email testing. You can easily send test emails for your campaigns and flows to a specific email address or a group of recipients, allowing you to check design, content, and links. Additionally, Klaviyo's A/B testing functionality, which is robust, lets you experiment with different subject lines, send times, and content variations to see what resonates best with your audience. This helps in optimizing engagement metrics, which indirectly contribute to a positive sender reputation.
The platform's segmentation capabilities also play a crucial role in deliverability. By segmenting your audience based on engagement, purchase history, or other behaviors, you can ensure you're sending relevant content to interested recipients. This practice helps reduce spam complaints and unsubscriptions, which are key signals to Internet Service Providers (ISPs) about your sending practices. Klaviyo’s analytics provide insight into open rates, click rates, and bounce rates, offering a glimpse into how your emails are performing post-delivery.
While Klaviyo’s internal tools are excellent for optimizing campaign performance and understanding recipient engagement, they have limitations when it comes to true deliverability testing. They can't tell you if your emails are hitting the spam folder on various email clients (Gmail, Outlook, Yahoo, etc.), whether your IP address or domain is on a blocklist, or if your email authentication records (SPF, DKIM, DMARC) are configured correctly. For those deeper insights, you need a dedicated deliverability testing platform.
Beyond Klaviyo: why third-party platforms are essential
To get a complete picture of your email deliverability, especially when sending through a platform like Klaviyo, external third-party tools are indispensable. These platforms specialize in simulating email delivery across a wide array of inbox providers, identifying potential spam folder placements, and alerting you to critical issues like blocklist appearances. They provide a crucial layer of insight that goes beyond the analytics offered by your ESP.
One of the most commonly mentioned platforms for deliverability testing, particularly for those on a tighter budget, is GlockApps. It's known for its straightforward seed testing, which allows you to see where your emails land across various mailbox providers. While GlockApps is a good starting point for basic checks, users often find it bare bones compared to more comprehensive solutions.
For those seeking more advanced features and deeper insights into their email deliverability, platforms like Inbox Monster, Validity (with its Everest product), and MailMonitor offer a much broader scope. These tools provide extensive inbox placement testing, spam filter diagnostics, sender reputation monitoring, and competitive intelligence. They are often considered enterprise-level solutions due to their robust feature sets and higher price points, making them ideal for businesses with significant email volume and a need for granular data.
Basic testing
Primarily offers seed list testing to see inbox placement across various ISPs.
Cost-effective
Generally a more affordable option, suitable for smaller operations or those new to dedicated deliverability testing.
Limited diagnostics
Provides less detail on why emails go to spam or specific authentication failures beyond a simple pass/fail.
Priced for larger businesses or those with complex deliverability needs, offering significant ROI through improved performance.
Actionable insights
Provides deep analysis and actionable recommendations to resolve deliverability issues, including detailed reports on email authentication.
What to look for in a deliverability testing solution
When evaluating deliverability testing platforms to complement your Klaviyo setup, several key features should be at the top of your list. First and foremost is inbox placement testing. This feature sends your email to a seed list of addresses across major ISPs (like Gmail, Outlook, Yahoo, and others) and reports back where your email landed, whether it was the inbox, spam folder, or was blocked entirely. This gives you a real-time snapshot of your deliverability health. You should also look for a tool that offers detailed insights into specific spam filter triggers, helping you fine-tune your content and sending practices.
Another crucial aspect is blocklist monitoring(or blacklist monitoring). These tools constantly check various public and private blocklists to see if your sending IP or domain has been listed, which can severely impact your deliverability. Comprehensive reporting on email authentication (SPF, DKIM, DMARC) is also vital, as misconfigurations in these records can lead to emails being rejected or sent to spam. Look for platforms that offer clear, actionable recommendations based on their findings.
Beyond the core testing features, consider the platform's user interface, ease of integration with your existing Klaviyo workflows, and the level of support provided. Some platforms may offer competitive intelligence, allowing you to compare your deliverability against industry benchmarks or competitors. Choosing a tool with strong analytics and reporting features will enable you to monitor trends over time and proactively address any emerging deliverability issues, ensuring your Klaviyo campaigns consistently reach your audience.
Choosing the right deliverability tool
Prioritize inbox placement testing: Ensure the tool tests across a diverse range of ISPs and global locations.
Look for comprehensive reporting: Detailed insights into spam filter hits, authentication issues, and blocklist status.
Consider your budget and needs: Basic seed testing tools are fine for starters, but robust platforms are worth the investment for high-volume senders.
Evaluate ease of integration: The tool should fit seamlessly into your existing Klaviyo workflow.
Feature
Description
Benefit for Klaviyo Users
Inbox placement testing
Sends emails to seed lists on various ISPs to report inbox, spam, or missing.
Directly identifies if your Klaviyo emails are reaching the primary inbox for key providers.
Spam filter diagnostics
Analyzes email content and headers against common spam filters.
Helps you refine your email copy and design within Klaviyo to avoid being flagged as spam.
Crucial for preventing widespread delivery failures that affect all your Klaviyo sends.
Authentication checks
Verifies SPF, DKIM, and DMARC record configurations.
Ensures your Klaviyo emails are properly authenticated, building trust with ISPs.
Reputation tracking
Monitors your sender score and domain reputation over time.
Provides a long-term view of your sending health beyond individual Klaviyo campaigns.
Integrating testing into your Klaviyo strategy
Integrating deliverability testing into your Klaviyo workflow doesn't have to be complicated. The most common approach is to use a seed list provided by your chosen deliverability platform. You'll add these seed email addresses as a segment or list within Klaviyo. Then, for each campaign or flow you want to test, you send a test email to this seed list from within Klaviyo. The deliverability platform then analyzes where these emails land and provides a detailed report.
Once you receive the test results, it's time for action. If emails are consistently landing in spam folders or being blocked, the report will often point to the likely culprits. This could range from content issues (e.g., using spammy keywords or too many images), sender reputation problems (due to high bounce rates or complaints), or technical misconfigurations in your email authentication records. Address these issues promptly, make adjustments in your Klaviyo campaigns or DNS records, and then re-test.
Regular, proactive testing is key to maintaining strong email deliverability. Don't just test when you notice a problem; make it a routine part of your email marketing strategy. This continuous monitoring, combined with Klaviyo’s own engagement analytics, will give you the most comprehensive understanding of your email performance and help you adapt to evolving ISP requirements, such as those from Gmail and Outlook. Consistent testing and optimization are essential for maximizing the reach and effectiveness of your Klaviyo campaigns.
Views from the trenches
Best practices
Maintain a clean email list by regularly removing unengaged subscribers and invalid addresses.
Segment your audience effectively in Klaviyo to send highly relevant content, improving engagement metrics.
Routinely monitor your sender reputation using tools like Google Postmaster Tools.
Common pitfalls
Solely relying on Klaviyo's internal metrics without using external deliverability testing tools.
Ignoring soft bounces, which can indicate emerging deliverability issues or recipient engagement problems.
Sending emails to purchased or old lists, which are often riddled with spam traps and invalid addresses.
Expert tips
Use a diverse set of seed list accounts in your deliverability testing tool to get a realistic picture across various ISPs.
Pay close attention to Gmail and Yahoo's updated sender requirements, as they significantly impact deliverability.
Combine automated testing with manual checks, like sending test emails to a personal inbox on different email clients.
Marketer view
A marketer from Email Geeks says that GlockApps is not bad and could be the cheapest option available for deliverability testing.
2023-12-12 - Email Geeks
Marketer view
A marketer from Email Geeks says that if cost is not an issue, Inbox Monster is the preferred choice for deliverability testing.
2023-12-12 - Email Geeks
Ensuring your emails reach their destination
Mastering email deliverability with Klaviyo goes beyond simply sending campaigns. It requires a proactive approach that leverages both Klaviyo's native strengths and the advanced capabilities of third-party testing platforms. While Klaviyo offers valuable tools for campaign optimization and engagement analysis, dedicated deliverability tools provide the crucial insights needed to understand how your emails are truly performing across the complex landscape of mailbox providers and spam filters.
By investing in the right deliverability testing platform and regularly integrating it into your Klaviyo strategy, you can identify and resolve issues before they impact your sender reputation and campaign ROI. This combination ensures your valuable messages consistently reach the inbox, maximizing the effectiveness of your email marketing efforts and driving better results for your e-commerce business.
