Testing email deliverability ensures your messages reach the primary inbox instead of spam folders. Even with a high delivery rate, emails can still be flagged as spam, impacting engagement and sender reputation. Here's what you need to know:
Maintain strong deliverability by regularly testing, cleaning your email list, and monitoring metrics like bounce rates (<2%), spam complaints (<0.1%), and inbox placement (>90%). Tools like Mailforge or Google Postmaster Tools can simplify setup and tracking. Deliverability isn’t a one-time task - it’s an ongoing effort to keep your campaigns effective.
Once you understand how spam filters evaluate emails, the next step is to test email deliverability systematically. This helps identify where your emails land and uncover the causes behind any issues. Here are three key methods every sender should consider.
Inbox placement testing shows where your emails end up - whether in the primary inbox, spam folder, or elsewhere - across various email providers. It helps you gauge your sender reputation and see how different email clients handle your messages.
Start by creating a small test list that includes addresses from major providers like Gmail, Yahoo, and Outlook. Send test emails that match your actual campaigns in terms of content, subject lines, and design. This approach replicates real-world performance.
Once the test emails are sent, track their placement within each recipient's inbox. Key metrics to monitor include:
Tools like Litmus, GlockApps, and Email on Acid can provide detailed data on how your emails perform across different platforms. Based on the results, you can make adjustments - whether that’s refining your content, updating authentication settings, or cleaning your email list. The ultimate goal is to increase the number of emails reaching the primary inbox while reducing spam placements.
Spam filter simulations are a proactive way to catch deliverability problems before they affect your campaigns. These tools mimic how major providers like Gmail and Outlook evaluate your emails, flagging potential issues with content, structure, or authentication.
To run a simulation, send a test email to the tool’s designated address. The tool will analyze it for spam triggers, authentication errors, and inbox placement results. For example, platforms like MailGenius can identify broken code, authentication gaps, or problematic content. Their reports also offer actionable tips to improve your email's chances of landing in the inbox.
The importance of this method is clear when you consider how different setups can yield vastly different results. In one test using the same template and shared IPs, one email service provider achieved a 78.8% inbox placement rate, while another managed only 61.0%. This underscores the need to test your specific combination of content and infrastructure.
Authentication checks are all about proving your emails are legitimate. When properly set up, authentication protocols like SPF, DKIM, and DMARC help ensure your emails are recognized as authentic by receiving servers.
Issues with authentication records - whether they’re missing, misconfigured, or inconsistent - are a common cause of deliverability problems. Without proper authentication, email providers may flag your messages as suspicious and route them to spam folders.
Most deliverability tools include authentication verification as part of their analysis. These tools check that your SPF, DKIM, and DMARC records are correctly configured and offer recommendations for fixing any problems. Regular testing is especially important if you use shared infrastructure or make changes to your email setup. Even minor configuration errors can hurt your deliverability.
Now that you’re familiar with the testing methods, let’s dive into how to put them into action. This guide will walk you through the process of systematically testing your email deliverability and identifying areas that need improvement.
The first step is to establish a solid email infrastructure that supports high deliverability and smooth testing.
| Setup Type | Best For | Pros | Cons |
|---|---|---|---|
| On-Premises | Regulated industries, IT-heavy teams | Full control, internal security | Expensive, slow to scale, high setup cost |
| Cloud-Based | Startups, cold emailers | Fast setup, no maintenance, scalable | Less control, shared infra risk |
| Hybrid | Enterprises with compliance needs | Flexibility + external scale | Complex to manage, needs internal ops |
For most businesses, cloud-based solutions strike the right balance between speed and functionality. A tool like Mailforge simplifies domain setup and authentication, ensuring your test campaigns begin on solid footing. It automates DNS configuration, including critical authentication records like SPF, DKIM, and DMARC.
Karlo Binda, Founder of Leadsnack.co, highlights the time savings:
"Procedures that usually took hours (setting DKIM, SPF, etc. records) for multiple domains, now take a few minutes. Mailforge is also cost-efficient since you spend per mailbox ~3 times less than with Gmail".
For example, Mailforge costs $484 per month for 200 mailboxes, whereas Google Workspace costs $1,680, and Microsoft 365 costs $1,200.
Another key decision is whether to use shared or dedicated IP addresses. Shared IPs are ideal for low-volume senders since they don’t require warming up, but your reputation can be affected by other users. Dedicated IPs, on the other hand, give you full control over your reputation but require careful warmup and are better suited for high-volume campaigns.
Finally, create a test list that includes major providers like Gmail, Yahoo, Outlook, and Apple Mail, as well as any niche providers your audience might use. This ensures your tests reflect actual performance across different filtering systems. Once your infrastructure is ready, start with small-scale tests to validate your setup.
With your infrastructure in place, begin testing with small-scale campaigns that closely mirror your actual email content and sending patterns. Tools like Mail-Tester make this easy - simply send a test email to the address they provide, and you’ll get a score that indicates how likely your email is to land in the spam folder.
Before scaling up, check for these issues:
As you test, monitor these key metrics:
Remember, each email provider uses unique filtering algorithms, so track these metrics across multiple platforms. Tools like Google Postmaster Tools can help you monitor your sending reputation and deliverability performance, especially for Gmail.
After running your test campaigns, consolidate the results to identify areas for improvement. On average, 19% of emails either go missing or are caught by spam filters, and 70% of emails have at least one spam-related issue. Start by reviewing your Mail-Tester results to pinpoint issues such as missing authentication records, problematic content triggers, or formatting errors.
Carin Slater, Manager of Lifecycle Email Marketing at Litmus, stresses the importance of engagement:
"It's important not to overuse spammy words, of course, but what really matters is that your subscribers want to receive the emails you're sending. That they're actively engaging with your content. If an ISP sees that nobody's interacting with your emails, they're going to say, 'Nobody wants this. Must be spam'".
Here are some strategies to improve your email deliverability:
As Carin Slater notes:
"Everyone's goal is obviously 100%. What we focus on is our inbox placement. We want 100% of our emails getting to the inbox, and if it drops below 90%, we're going to immediately investigate what's going on".
Marketers who monitor deliverability and inbox placement are 22% more likely to have successful email programs. Testing and optimization are not one-time tasks - they should be part of an ongoing process.
Rob Pellow, Digital Experience Director at Armadillo, underscores the importance of vigilance:
"An IP reputation is hard to build, easy to lose, and hard to regain. Therefore, ensuring you are sending the best emails before they are sent will limit the damage caused, and monitoring, post-send, will allow fine-tuning - and it will allow you to know when further action needs to be taken to protect or improve your IP status".
Once you've fine-tuned your email tests, the work doesn’t stop there. Keeping your emails in inboxes requires constant attention. Email providers regularly tweak their filtering systems, and your sender reputation can shift based on how you operate over time. Here’s how to ensure your emails continue to land where they should.
Deliverability problems can crop up even after a strong start. One frequent culprit? Authentication failures. These often happen when DNS records like SPF, DKIM, or DMARC expire or are altered during website updates. To avoid this, review your authentication settings at least quarterly using your email platform’s tools.
Another issue is blacklisting. High complaint rates or sending emails to invalid addresses can land your domain or IP on spam blacklists, which directly harms your sender reputation. Similarly, list hygiene tends to decline over time. A bounce rate over 2% signals a problem with list quality that needs immediate attention. If spam complaints exceed 0.1%, it’s time to rethink your content or how you’re acquiring email subscribers. And if engagement is dropping, it might mean your content isn’t hitting the mark or you’re emailing too often. Regularly clean your list and try to re-engage inactive subscribers to keep your performance on track.
Tim Kauble, Senior Director of Deliverability & Compliance Operations at Salesforce, highlights the stakes: "If you focus on optimizing for delivery, you inherently maximize your opportunities for ROI."
For businesses using shared email platforms like Mailforge, reputation management becomes even more critical. While these platforms handle technical tasks like DNS setup and IP warming, your sending habits still play a key role in your reputation within the shared network.
To maintain long-term deliverability, track the right metrics. Your inbox placement rate should stay above 90%. If it dips below that, investigate immediately to prevent larger issues from affecting your campaigns.
Bounce rates also act as an early warning system. Hard bounces should remain under 2%; anything higher can hurt your standing with email providers. Spam complaint rates, another key metric, should stay below 0.1%. Keep in mind that 54% of users report emails as spam if they didn’t consent to receive them, and 49% complain if there’s no easy way to unsubscribe.
| Metric | Healthy Range | Warning Signs | Action Required |
|---|---|---|---|
| Inbox Placement | Above 90% | 85–90% | Below 85% |
| Bounce Rate | Below 2% | 2–5% | Above 5% |
| Spam Complaints | Below 0.1% | 0.1–0.3% | Above 0.3% |
Carin Slater, Manager of Lifecycle Email Marketing at Litmus, stresses the importance of vigilance: "Everyone's goal is obviously 100%. What we focus on is our inbox placement. We want 100% of our emails getting to the inbox, and if it drops below 90%, we're going to immediately investigate what's going on. Deliverability is a measure of the health of your email marketing program, so it's important to do regular check-ups on your domain, IP, and authentication in particular to make sure you're up-to-date, just like how we all go to the doctor each year."
Feedback loops from major email providers can also be incredibly helpful. These notify you when recipients mark your emails as spam, giving you the chance to remove those users and adjust your approach.
Tracking metrics can help you spot issues, but staying compliant is what prevents them in the first place. Accurate authentication records and regular monitoring are key to staying within email marketing laws, which are as much about maintaining deliverability as they are about avoiding fines. In the U.S., the CAN-SPAM Act lays out specific requirements for all commercial emails.
Consent is the cornerstone of compliance. Whenever possible, use double opt-in to confirm that subscribers genuinely want to hear from you. Keep detailed records of when and how people signed up. Every email should include a clear unsubscribe link, and requests to opt out should be processed promptly to avoid frustration or complaints. Additionally, include a valid physical address in your emails to meet legal standards and build trust.
Content plays a big role here, too. Be upfront about promotional content, avoid misleading subject lines, and ensure your emails align with what your subscribers signed up for.
The Federal Trade Commission explains: "The CAN-SPAM Act, a law that sets the rules for commercial email, establishes requirements for commercial messages, gives recipients the right to have you stop emailing them, and spells out tough penalties for violations."
Data protection is just as important. Be transparent about how you collect, store, and use subscriber information. If you work with third-party vendors, make sure they follow compliance standards as well.
Carin Slater underscores this point: "You're a guest in your subscriber's inboxes, so respect what they have told you. Whether that's their overall preferences and topics, or if they say they want their emails in Dark Mode, or they sign up for your newsletter and nothing else, you have to honor that."
Conduct regular compliance audits to review your opt-in processes, unsubscribe mechanisms, and email content. As privacy laws evolve, staying informed will help protect both your deliverability and your reputation.
Email deliverability testing isn’t a one-and-done task - it’s an ongoing effort that directly impacts the success of your outreach. With an average deliverability rate of 81%, nearly one in five emails never makes it to the recipient’s inbox. This highlights why having a structured testing process is so important.
A strong foundation for deliverability starts with technical authentication. By setting up SPF, DKIM, and DMARC records, you establish your credibility with email providers and protect your domain from being misused.
The quality of your email list is just as important. Organic lists consistently perform better, delivering five times higher open rates and four times fewer spam complaints. Regularly cleaning your list - removing hard bounces, inactive subscribers, and spam traps - helps protect your sender reputation and boosts inbox placement.
First impressions matter too. With 68% of Americans deciding whether to open an email based on the "From" line, using a consistent sender name builds trust and recognition. On top of that, steering clear of spammy trigger words and crafting personalized, relevant content signals to email providers that your messages are genuinely wanted. These practices ensure you’re always improving and staying ahead.
Consider some key performance metrics: welcome emails have an impressive 86.03% open rate, but subscribers spend just 8.97 seconds on average reading an email. This means every detail - from the subject line to the body content - needs to be optimized for quick readability and engagement.
Monitoring your performance is essential. Email lists naturally degrade by 22.5% each year, so consistent tracking and maintenance are non-negotiable. If your inbox placement rate dips below 90%, it’s time to act fast to prevent small issues from spiraling into bigger problems. For growing businesses, sticking to these basics becomes even more critical.
As mentioned earlier, consistent testing and optimization are key to staying effective. Platforms like Mailforge can simplify technical tasks like DNS setup and IP warming, but your sending habits ultimately determine your success. Whether you’re reaching out to a small group of contacts or managing campaigns across thousands of domains, the core principles remain the same: authenticate your emails, keep your lists clean, send content people care about, and track your performance regularly.
Done right, email deliverability testing can yield a return of $36 for every $1 spent. By following a systematic approach and sticking to proven best practices, you can make sure your outreach efforts deliver the results you’re aiming for.
To ensure your emails land in inboxes and not spam folders, start by setting up SPF, DKIM, and DMARC records. These authentication protocols safeguard your domain's reputation and signal to email providers that your messages are trustworthy.
Keep your sender reputation intact by steering clear of spammy phrases, avoiding purchased email lists, and only contacting people who have given clear consent to receive your emails. Regularly warming up your email account and segmenting your audience can also lower the risk of being flagged as spam.
For those scaling email campaigns, tools like Mailforge can make managing multiple domains and mailboxes much easier. With features like automated DNS setup and enhanced deliverability options, you’ll have the tools needed to boost your email performance.
When multiple senders use the same IP address, it's called a shared IP address. With this setup, the sender reputation is shared among all users. While this can lower the chances of being blacklisted, your email deliverability might be affected by the actions of others sharing the IP.
A dedicated IP address, however, is reserved for a single sender. This gives you full control over your sender reputation, which can improve email deliverability - especially for large-scale campaigns. But keep in mind, maintaining a strong reputation requires consistent email activity. Irregular sending patterns could raise red flags and potentially lead to spam issues.
To keep your email deliverability on point, make it a habit to check and update your email authentication settings every 6 to 12 months. This ensures your SPF, DKIM, and DMARC records stay accurate and match any updates to your email-sending domains or infrastructure.
By doing this regularly, you can also catch and fix potential problems, like outdated DNS records or shifts in email provider policies, that might otherwise hurt your deliverability.