How Email Deliverability Testing Works
Want your emails to land in inboxes, not spam? Email deliverability testing ensures your messages reach their destination and engage recipients. Here's what matters most:
- Deliverability Testing checks sender reputation, authentication (SPF, DKIM, DMARC), content quality, and engagement metrics.
- Key Metrics include delivery rate (98%+ is ideal), bounce rate (<0.1%), inbox placement (85%+), and spam complaints (<0.08%).
- Authentication Protocols like SPF, DKIM, and DMARC are crucial for building trust with email providers.
- Testing Methods: Use pre-send testing (simulate delivery) and post-send monitoring (track real-world performance).
Skipping this process risks lost revenue, damaged reputation, and missed opportunities. Tools like Mailgun Optimize and GlockApps help automate testing, while proper setup of DNS records ensures smooth delivery.
Bottom Line: Regular testing and monitoring are your best defense against spam filters and delivery issues.
Key Metrics in Email Deliverability Testing
These metrics are the foundation of any effective email strategy, ensuring your messages not only reach their intended destination but also engage your audience. By analyzing these numbers, you can get a full picture of how your campaigns perform - from successful delivery to recipient interaction.
Delivery Rate and Bounce Rate
Delivery rate tracks the percentage of emails accepted by receiving mail servers, regardless of whether they land in the inbox or another folder. A solid delivery rate hovers around 98%. If your rate drops below 80%, it’s a major warning sign. For instance, if you send 1,000 emails and 950 are accepted, your delivery rate is 95%.
Bounce rate, on the other hand, measures the percentage of emails that fail to deliver. There are two types of bounces:
- Hard bounces: These occur when the email address is invalid, nonexistent, or the domain is permanently unreachable.
- Soft bounces: These are temporary issues like full inboxes, server downtime, or exceeding message size limits.
To stay in good standing, Google advises keeping your bounce rate below 0.1%. A high bounce rate often points to poor list management and can tarnish your sender reputation, potentially leading to blocks by major email providers.
Inbox Placement and Spam Complaint Rate
Inbox placement rate shows the percentage of emails that actually land in the primary inbox, where they’re most likely to be seen.
"Inbox placement is harder to measure than overall delivery because receiving mail servers will frequently indicate that mail has been delivered, when it has not actually been placed in the inbox."
– Return Path
A strong inbox placement rate is at least 85%, with 98–99% being the ideal range. If this rate falls below 70%, it signals significant issues. In January 2024, the average deliverability rate across email service providers was 83.1%, meaning nearly one in five marketing emails missed the primary inbox.
Spam complaint rate measures how often recipients mark your emails as spam. This is a critical metric since it reflects how your audience perceives your content. Gmail recommends keeping spam complaint rates below 0.1%, and anything above 0.3% could result in blocked sends. Ideally, aim for a spam complaint rate under 0.08%. Even slight increases can lead to penalties, pushing future emails into spam folders.
To evaluate inbox placement accurately, use seed list testing. This involves sending campaigns to test accounts across providers like Gmail, Outlook, Yahoo, and Apple Mail. Tools such as Mailgun Optimize, GlockApps, and MailTester can automate this process, offering detailed placement reports. Seed list testing helps verify your metrics and ensures your campaigns are on track.
Engagement Metrics: Open and Click-Through Rates
Beyond delivery stats, engagement metrics provide valuable insights into how recipients interact with your emails. These metrics are often early indicators of deliverability health, as email providers monitor recipient behavior closely.
Open rates represent the percentage of delivered emails that recipients open. According to Klaviyo’s Q3 2023 data, the average open rate for campaigns was 43.33%, while automated flows saw 55.21%. A good benchmark for open rates is between 20–30%, though privacy measures like Apple’s Mail Privacy Protection can affect accuracy.
Click-through rates (CTR) measure the percentage of recipients who click links within your emails. Klaviyo reports an average CTR of 1.44% for campaigns and 5.37% for flows. Strive for a CTR of 5% or higher, with rates above 8% being exceptional.
High engagement sends a message to email providers that your content is relevant and valuable.
| Metric | Benchmark | Calculation | Impact |
|---|---|---|---|
| Delivery Rate | 90–98% | (Emails delivered ÷ Total sent) × 100 | Server acceptance |
| Bounce Rate | <0.1% | Derived from the delivery rate | Sender reputation |
| Inbox Placement Rate | 85%+ (98–99% ideal) | (Emails in inbox ÷ Emails delivered) × 100 | Actual visibility |
| Spam Complaint Rate | <0.08% | (Spam complaints ÷ Emails delivered) × 100 | Provider trust |
| Open Rate | 20–30% | (Emails opened ÷ Emails delivered) × 100 | Engagement signal |
| Click-Through Rate | 5%+ (8%+ outstanding) | (Clicks ÷ Emails delivered) × 100 | Content effectiveness |
Interestingly, only about 13% of senders use inbox placement testing to assess deliverability, meaning most marketers miss out on critical insights about their campaigns. By consistently tracking these key metrics, you can catch issues early and maintain a strong delivery performance over time.
Authentication Protocols and Sender Reputation
Email authentication protocols and sender reputation play a critical role in determining whether your emails land in recipients' inboxes or end up blocked. These protocols help establish trust and influence inbox placement. Let’s dig into how you can implement these protocols and keep an eye on their impact on sender reputation.
SPF, DKIM, and DMARC Records
SPF (Sender Policy Framework) lets domain owners specify which mail servers are allowed to send emails on their behalf. This helps prevent spoofing attempts. When an email is received, the server checks the SPF record to confirm that the sender is authorized.
DKIM (DomainKeys Identified Mail) adds a digital signature to your emails. This signature ensures the message hasn’t been tampered with during transit and verifies the sender’s identity. It’s like sealing a letter with a wax stamp - proof that it’s authentic and untouched.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) takes things a step further by combining SPF and DKIM. It allows domain owners to set rules for handling emails that fail authentication and provides reports on any issues. Without valid SPF or DKIM records, DMARC policies can flag your messages as spam, increasing the risk of delivery issues.
To ensure your DNS records are set up correctly, tools like MxToolbox or Mailtrap can help verify your configurations. For businesses managing multiple domains, manual setup can be a hassle. As Danny Goff, Director of Sales at Propeller, explains:
"Procedures that usually took hours (setting DKIM, SPF, etc. records) for multiple domains, now take just a few minutes."
Platforms like Mailforge simplify the process by automating DNS setup for SPF, DKIM, and DMARC. This makes it possible to configure authentication for hundreds - or even thousands - of domains and mailboxes quickly, while maintaining consistency across all domains.
Monitoring Domain and IP Reputation
Once your authentication protocols are in place, keeping tabs on your domain and IP reputation is crucial. Sender reputation is influenced by factors like authentication, sending history, user engagement, and spam complaints. A strong reputation increases the chances of your emails reaching inboxes, while a weak one can lead to delivery issues or your messages being flagged as spam. Reputation is fluid and can shift based on recent activity, such as high bounce rates or spam complaints.
Deliverability tools can help you monitor your domain and IP reputation. They check your details against blocklists, analyze past performance, and track metrics like bounce rates and spam complaints. Some tools even scan your domain against over 60 blocklists to assess your standing. If your domain or IP ends up on a blocklist, even important emails like password resets may fail to reach their destination.
To maintain a strong sender reputation, follow these best practices:
- Regularly review your authentication records and update them after any changes to your sending infrastructure.
- Monitor blocklists and remove flagged domains or IPs promptly.
- Clean your email list by removing inactive or outdated contacts.
- Track engagement metrics like open and click-through rates.
- Address any spikes in bounce rates or spam complaints immediately.
| Protocol | Purpose | Key Benefit |
|---|---|---|
| SPF | Verifies authorized sending servers | Helps prevent spoofing and improves delivery |
| DKIM | Adds a cryptographic signature to emails | Ensures message integrity and builds trust |
| DMARC | Aligns SPF/DKIM and sets handling policies | Protects against unauthorized use and provides insights |
Many businesses now take a dual approach: using pre-send testing to catch authentication issues before launching campaigns and post-send monitoring to track inbox placement and engagement. By integrating these steps into your overall deliverability strategy, you can maintain consistent inbox performance and avoid unnecessary delivery headaches.
Methods for Testing Email Deliverability
Ensuring your emails reach their intended recipients involves both proactive measures and ongoing monitoring. The two primary approaches - pre-send testing and post-send monitoring - work hand in hand to maintain strong inbox placement rates.
Research shows that marketers who use both methods are 22% more successful in maintaining deliverability. This demonstrates the importance of a well-rounded strategy.
Pre-Send Testing
Think of pre-send testing as your safety net before launching a campaign. By simulating email sends to curated seed lists (covering major providers like Gmail, Yahoo, and Outlook), you can predict whether your messages will land in the inbox, spam folder, or promotions tab[23,25].
This step also identifies potential issues in your email content. Spam filters can be triggered by various factors, such as poorly configured authentication settings (SPF, DKIM, DMARC), excessive use of spammy keywords, or an unbalanced image-to-text ratio[22,27]. Even small formatting errors can raise red flags.
To address these issues, tools like inbox placement testers and spam score analyzers are invaluable. For example, platforms like ZeroBounce and GlockApps simulate inbox placement, while services like MxToolbox validate your DNS and authentication configurations[21,22,25]. Some tools even check your sending domains against over 60 blocklists to ensure your emails aren’t blocked before they reach their destination.
By resolving any flagged issues during pre-send testing, you can launch your campaign with confidence. Once your emails are sent, the focus shifts to monitoring their actual performance.
Post-Send Monitoring
Post-send monitoring offers insights into how your emails perform in the real world. This includes tracking metrics like inbox placement rates, bounce rates, spam complaints, and engagement levels[21,24,26].
These metrics can reveal emerging deliverability challenges. For instance, a bounce rate above 5% or a spam complaint rate exceeding 0.08% signals potential problems that could hurt your sender reputation. Additionally, analyzing engagement trends can guide future campaigns - emails that consistently generate strong engagement are more likely to bypass spam filters, while underperforming ones might get flagged.
| Testing Method | Primary Purpose | Key Benefits | Usage Timing |
|---|---|---|---|
| Pre-Send Testing | Prevent deliverability issues | Detects problems before launch, validates authentication | Before campaign deployment |
| Post-Send Monitoring | Track real-world performance | Measures actual results, identifies trends, guides optimization | After campaign launch and ongoing |
For businesses managing large-scale email operations, platforms like Mailforge simplify the process by automating tasks such as domain and mailbox setup, DNS configuration, and bulk updates. This automation ensures smooth operations across numerous domains.
How to Set Up Email Deliverability Testing
Getting your emails to land in the inbox instead of the spam folder requires more than just hitting "send." Setting up email deliverability testing involves a step-by-step process that combines proper domain authentication with strategic testing methods. Here's how you can ensure your emails reach their intended audience.
Configuring Domains and Authentication
The foundation of email deliverability lies in setting up your domains with the right authentication protocols: SPF, DKIM, and DMARC. These help meet security standards set by major email providers.
Setting Up SPF Records
Start by identifying all the services that send emails on your behalf, like marketing platforms, CRMs, or internal servers. Then, log into your DNS provider to add or update TXT records. For example, if you're using Google Workspace, your SPF record might look like this: v=spf1 include:_spf.google.com ~all. Keep in mind that SPF records have a 10 DNS lookup limit - exceeding it could lead to PermErrors, which negatively affect deliverability.
Implementing DKIM Authentication
Enable DKIM through your email platform - services like Google Workspace and Microsoft 365 make this straightforward. Once activated, your platform will generate a public DKIM key. Publish this key as a TXT record in your DNS under a selector like default._domainkey.yourdomain.com or s1._domainkey.yourdomain.com. After publishing, test it by checking email headers for a valid DKIM signature.
Establishing DMARC Policy
Before diving into DMARC, ensure both SPF and DKIM are properly configured. Start with a monitoring policy (p=none) to gather data without affecting email delivery. For instance, you could publish the following TXT record under _dmarc.yourdomain.com:
v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com
Research indicates that many domains with DMARC records struggle to enforce policies effectively, but moving to a p=reject policy can improve deliverability by over 10% with major providers. Keep in mind that DNS changes may take anywhere from a few minutes to 48 hours to propagate globally.
Once your authentication protocols are set, you can move on to testing how your emails perform in real-world scenarios using seed lists.
Using Seed Lists and Analyzing Results
Seed lists are a valuable tool for evaluating email performance across different providers before launching a full campaign.
Creating and Implementing Seed Lists
A seed list is essentially a group of monitored test email addresses across providers like Gmail, Yahoo, and Outlook. Depending on your goals, you can choose between several testing methods:
- Manual Testing: Ideal for one-time campaigns, such as promotional emails, where you can test specific spam filters and email services.
- Automatic Testing: Best for campaigns with static content, like triggered or cold outreach emails, allowing for daily monitoring and alerts.
- Proxy Testing: Combines manual testing with an intermediate email address that forwards messages to the seed list, helping track sender scores and delivery times.
Interpreting Seed List Results
A solid inbox placement rate is generally 80% or higher. High spam folder placement indicates potential issues with your reputation or email content, while missing emails could signal bounces or ISP blocks. Here's a quick breakdown:
| Result Category | What It Indicates | Action Required |
|---|---|---|
| 80%+ Inbox Placement | Strong sender reputation; content passes filters | Proceed with campaign launch |
| High Spam Placement | Reputation or content issues detected | Review content and authentication settings |
| Missing Emails | Bounces or blocks occurring | Investigate technical setup and message content |
That said, seed list testing has its limitations, especially in B2B environments. Experts note that seed lists often underreport spam placement rates for B2B emails, as seed accounts lack the engagement history and complex filtering used by large enterprises.
Using Mailforge for Testing
Once your domain configurations and seed list testing are in place, automation tools like Mailforge can simplify the process and save time.
Automated Setup Process
Mailforge streamlines your deliverability testing by automating tasks like domain setup and DNS configuration. Start by using its Domain Calculator to determine your sending capacity based on your email volume. Then, navigate to Domains → Auto Generate Domains to purchase and configure domains. Mailforge automatically updates your nameservers, handles DKIM and SPF setup, and creates inboxes.
"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. The support team replies in minutes and is happy to sort out issues in a proactive manner!"
Cost and Infrastructure Benefits
Mailforge offers affordable pricing, starting at $30 per month for 10 mailboxes, with savings of up to three times compared to traditional providers. Its shared IP infrastructure is tailored for cold outreach, helping maintain a strong sender reputation.
Enhanced Security and Deliverability Features
Mailforge also includes optional add-ons like SSL and Domain Masking to enhance security and build trust. With a quick 5-minute setup and unlimited mailbox capabilities, the platform is especially valuable for agencies and businesses scaling their outbound efforts. As Isabella L., Founder of Let's Fearlessly Grow, shared:
"Operating in a high-growth startup environment requires speed, scalability, and operational efficiency. We needed to build an outbound motion that didn't break as we scaled - and Mailforge gave us that foundation."
For a complete deliverability testing solution, Mailforge integrates with Warmforge, which provides email warm-up and placement testing. Agencies managing multiple domains can benefit from bulk pricing, with costs as low as $3 per mailbox.
Optimizing Email Deliverability
Getting emails into inboxes isn’t a one-and-done task - it’s an ongoing process. The difference between a cold email campaign that thrives and one that flops often boils down to consistent monitoring and fine-tuning.
Laying the Groundwork for Success
Done right, email marketing can deliver an impressive return - up to $36 for every $1 spent - if your messages actually make it to the inbox. But here’s the catch: 70% of emails encounter at least one spam-related issue that can derail their delivery. That’s why regular optimization isn’t just helpful - it’s essential.
"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." - Carin Slater, Manager of Lifecycle Email Marketing at Litmus
Metrics That Matter Most
To keep your campaigns on track, monitor key metrics daily. For example, aim for a spam complaint rate below 0.1% and a bounce rate under 2%. If your inbox placement rate dips below 90%, it’s time to dig in and identify the problem.
Once you’ve got your daily metrics under control, set aside time for periodic audits to refine your strategy further.
A 90-Day Plan for Better Deliverability
A structured, 90-day optimization cycle can work wonders for deliverability. Start by auditing your email infrastructure - double-check your SPF, DKIM, and DMARC records. Next, clean up your list by removing inactive contacts from the past 90 days. Finally, test subject lines with personalized touches that reflect recipient behavior.
Avoiding Common Pitfalls
Issues like decayed lists and authentication errors can wreak havoc on your delivery rates, cutting them by as much as 30% and blocking 17% of cold B2B emails. To combat this, use double opt-ins, run re-engagement campaigns for inactive subscribers, and steer clear of purchased email lists.
Balancing Content and Authentication
Email providers are getting smarter at filtering messages. To stay ahead, ensure your text-to-image ratios are balanced, avoid spammy trigger words, and maintain strong authentication protocols. Adding BIMI (Brand Indicators for Message Identification) can also help - this simple step can increase open rates by up to 21%.
The Unique Challenge of Cold Emails
Cold email campaigns face extra hurdles since recipients haven’t explicitly opted in. Providers like Gmail and Microsoft have placed even greater importance on engagement metrics and spam reports in recent years. To succeed, you’ll need to warm up new domains carefully and stick to consistent sending patterns.
Building a Stronger Reputation
Your domain reputation now carries more weight than your IP reputation in most B2B scenarios. To build and maintain a positive reputation, focus on sending relevant, personalized content that aligns with recipient preferences. And when someone unsubscribes, act on it immediately - 49% of recipients will file a spam complaint if unsubscribing isn’t easy.
FAQs
How can I make sure my emails land in the inbox and not the spam folder?
To make sure your emails actually land in inboxes and not the dreaded spam folder, start by setting up the right DNS records - SPF, DKIM, and DMARC. These records act as proof that your emails are legitimate, reducing the chances of them being flagged as spam.
It’s also important to keep an eye on your domain’s health. Regular checks can help you avoid blacklisting and keep your sender reputation intact. Tools that test inbox placement and spam scores are a great way to spot and fix issues before they disrupt your email campaigns.
Platforms like Mailforge can make this process easier by automating DNS setup and optimizing deliverability. Staying proactive with testing and maintenance ensures your emails consistently hit the inbox where they belong.
What causes high email bounce rates, and how can you prevent them?
High email bounce rates often stem from invalid or non-existent email addresses, full inboxes, spam filters blocking messages, or technical problems on the recipient's server. These issues can damage your sender reputation and make it harder for your emails to reach their intended audience.
To reduce bounces, start by verifying your email list to confirm all addresses are active and accurate. Implementing a double opt-in process ensures new subscribers genuinely want to receive your emails, and regularly cleaning your list by removing addresses that consistently result in soft bounces is essential. On top of that, maintaining a strong sender reputation is key. This includes using proper email authentication methods like SPF, DKIM, and DMARC, and following best practices for cold email outreach to keep your bounce rates low.
How do SPF, DKIM, and DMARC protocols work together to enhance email deliverability?
SPF, DKIM, and DMARC are three key email authentication protocols that work together to safeguard your email domain and enhance delivery rates.
SPF (Sender Policy Framework) checks whether an email is sent from an authorized server, verifying that the sending IP matches what’s approved for your domain. DKIM (DomainKeys Identified Mail) attaches a digital signature to your emails, ensuring the content remains intact and hasn’t been altered during transmission. DMARC (Domain-based Message Authentication, Reporting, and Conformance) connects SPF and DKIM, instructing how to handle emails that fail authentication while providing detailed reports on unauthorized activities.
Using all three protocols helps protect against email spoofing, strengthens trust with email providers, and improves the chances of your emails landing in the inbox instead of the spam folder.