You know that sinking feeling when you realize your carefully crafted emails aren't reaching your customers? We've been there too.
Email deliverability checks test whether your emails reach inboxes or land in spam folders. These tests evaluate your email authentication setup (SPF, DKIM, DMARC), sender reputation, blacklist status, and spam score to show you exactly where your messages end up.
Think of it like a health checkup for your email marketing. Just like you wouldn't ignore warning signs about your physical health, you shouldn't ignore signs that your emails aren't getting delivered.
The good news? Testing your email deliverability is simpler than you might think. Most free email deliverability testing tools provide instant results without any complicated setup or technical knowledge required.
We'll walk you through what email deliverability checks actually measure, how to run these tests yourself, what your results really mean, and most importantly, how to fix any issues dragging down your inbox placement rate.
What Is an Email Deliverability Check?
An email deliverability check is a diagnostic test that shows you whether your emails successfully reach recipients' inboxes.
Here's what makes it different from just hitting "send" and hoping for the best. When you run a deliverability test, tools like MXToolbox and GlockApps assess key factors including email authentication (SPF, DKIM), domain reputation, and blacklist status.
Think of it as an x-ray for your email campaigns. You can't see what's happening behind the scenes without it.
The test evaluates multiple checkpoints that email service providers use to decide whether your message deserves inbox placement or should be filtered to spam. These checkpoints include your sender reputation, email authentication protocols, content quality, and whether your sending IP address appears on any blacklists.
Most deliverability checks work by having you send a test email to a designated address. The tool then analyzes that email from multiple angles and generates a detailed report showing potential problems.
What's particularly helpful? Many free email deliverability testing tools provide actionable insights immediately. No waiting around for days to figure out what's wrong.
What Deliverability Tests Actually Measure
Email deliverability tests examine several critical components that determine inbox placement.
First, they check your email authentication setup. This includes verifying that your SPF, DKIM, and DMARC records are properly configured in your DNS settings. Without these authentication protocols working correctly, email providers like Gmail, Outlook, and Yahoo will be skeptical about your messages.
Second, they analyze your content for spam triggers. This means scanning your subject line, body text, images, and links for elements that commonly appear in spam emails.
Third, they evaluate your sender reputation. Your reputation score is based on factors like bounce rates, spam complaints, engagement levels, and sending patterns. Think of it as your credit score for email marketing.
Fourth, they check blacklist status. If your sending IP address or domain appears on any major blacklists, your emails won't reach inboxes no matter how good your content is.
Understanding Your Deliverability Score
Here's something that surprises most people: not all deliverability tests provide a single numerical score.
Some tools like Clearout provide an AI-powered deliverability verdict or score for each email address, while others give you a breakdown of individual components without assigning an overall grade.
Why does this matter? Because email deliverability isn't really a single number. It's a combination of factors that work together.
When you do see a score, it typically reflects the probability that your emails will reach the inbox based on current authentication setup, content quality, and sender reputation. A score above 90% is generally excellent, while anything below 80% needs immediate attention.
The most valuable deliverability reports break down results by major email providers. Your emails might perform well with Gmail users but struggle to reach Outlook inboxes, for example.
Why Email Deliverability Matters for Your Business
Low email deliverability kills your marketing results before anyone even sees your message.
You could write the most compelling email copy in the world, design beautiful templates, and segment your list perfectly. But if your emails land in spam folders, none of that effort matters.
Industry benchmarks show that an acceptable deliverability rate is typically around 95%, and a bounce rate should not exceed 3%. If you're falling short of these numbers, you're leaving serious money on the table.
The Real Cost of Poor Deliverability
Poor email deliverability impacts your business in ways that go beyond just missed emails.
First, there's the direct revenue loss. If 30% of your promotional emails land in spam, you're effectively throwing away 30% of your email marketing budget and the potential revenue those campaigns would generate.
Second, poor deliverability damages your sender reputation over time. Email service providers track how recipients interact with your messages. Low open rates and high spam complaints create a negative feedback loop that makes future deliverability even worse.
Third, you waste resources on ineffective campaigns. Your team spends time creating content and managing campaigns that aren't reaching their intended audience.
Fourth, you miss opportunities to nurture customer relationships. When your emails don't arrive, customers miss important updates, special offers, and valuable content that would strengthen their connection to your brand.
How Deliverability Affects Sender Reputation
Your sender reputation works like a trust score that email providers assign to your domain and IP address.
Every email you send either strengthens or weakens this reputation. High engagement rates, low bounce rates, and few spam complaints improve your score. Poor practices damage it.
What makes sender reputation tricky? It's not immediately visible to you, but email providers rely on it heavily when deciding where your emails should land.
Monitoring your deliverability through regular testing helps you catch reputation problems early. If you notice your inbox placement rate dropping, you can investigate and fix issues before they cause serious damage.
Tools that focus on list hygiene, like ZeroBounce, identify and remove invalid, spam-trap, or inactive emails, which helps prevent bounces and protects sender reputation.
Key Factors That Affect Email Deliverability
Email deliverability depends on multiple factors working together correctly.
Understanding these factors helps you pinpoint exactly where problems occur in your email delivery process. Let's break down what actually impacts whether your messages reach inboxes.
Email Authentication Protocols
Email authentication proves to receiving servers that you're actually who you claim to be.
The three main authentication protocols are SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance). Each serves a specific purpose in verifying your identity as a legitimate sender.
SPF works by listing which mail servers are authorized to send emails from your domain. When an email arrives, the receiving server checks your SPF record to confirm the message came from an approved source.
DKIM adds a digital signature to your emails. This signature proves the message wasn't altered during transmission and actually came from your domain.
DMARC builds on SPF and DKIM by telling receiving servers what to do when authentication checks fail. It also provides reporting so you can monitor authentication issues.
Without proper authentication setup, your emails look suspicious to receiving servers. Major email providers like Gmail and Outlook increasingly require these protocols for reliable inbox placement.
Sender Reputation and IP Warming
Your sender reputation score determines how email providers treat your messages before recipients ever see them.
This score combines multiple signals including bounce rates, spam complaint rates, engagement metrics, and sending patterns. Email providers track these signals constantly and adjust their filtering decisions accordingly.
New sending IPs or domains start with no reputation, which is actually worse than having a poor reputation. Email providers don't trust unknown senders, so they often filter these messages more aggressively.
Email warmup services help build reputation gradually by slowly increasing your sending volume over time. Think of it like building credit history rather than maxing out a new credit card immediately.
Monitoring your sender reputation should be an ongoing practice, not something you check once and forget. Regular deliverability testing helps you spot reputation problems before they seriously impact your campaigns.
List Quality and Email Verification
The quality of your email list directly impacts your deliverability rate.
Invalid email addresses, spam traps, and inactive accounts all damage your sender reputation when you attempt to contact them. High bounce rates signal to email providers that you're not maintaining proper list hygiene.
Email verification tools help you identify problematic addresses before sending campaigns. These tools check whether email addresses actually exist, whether they're spam traps, and whether they're likely to engage with your messages.
At mailfloss, we automatically verify and clean your email lists daily. Our system runs over 20 checks on each email address and even fixes common typos in domains like Gmail, Hotmail, Yahoo, and AOL.
The 'set and forget' approach works best for busy professionals. Once you connect mailfloss to platforms like Mailchimp, HubSpot, or any of our 35+ supported email service providers, the cleaning happens automatically in the background.
Content Quality and Spam Filters
Your email content gets scrutinized by sophisticated spam filters looking for red flags.
These filters analyze your subject lines, body content, images, links, and overall structure. Certain words, phrases, and formatting patterns trigger spam scores that can land your messages in junk folders.
Common spam triggers include excessive capitalization, too many exclamation points, misleading subject lines, suspicious links, and overly promotional language. Using URL shorteners or including too many images without enough text can also raise red flags.
Email content analysis tools examine these elements and provide spam scores before you send campaigns. This lets you adjust problematic content and improve your chances of inbox placement.
The HTML structure of your emails matters too. Poorly coded templates, broken links, and images without alt text can all contribute to deliverability issues.
How to Test Your Email Deliverability Step by Step
Testing your email deliverability takes just a few minutes when you use the right approach.
We'll walk through the exact process for running a complete deliverability test. This works whether you're troubleshooting problems or just checking your current status.
Choosing the Right Deliverability Testing Tool
Different deliverability testing tools focus on different aspects of email delivery.
MXToolbox is best for quick, technical checks and blacklist monitoring, making it ideal when you need to verify DNS records or check if your IP address appears on any blacklists.
GlockApps provides detailed inbox placement testing across multiple email providers. This tool shows you exactly how Gmail, Outlook, Yahoo, and other major providers treat your emails.
For comprehensive list validation, ZeroBounce focuses specifically on identifying invalid, risky, or inactive email addresses in your database.
Most professionals use a combination of tools rather than relying on just one. Start with a general deliverability test, then use specialized tools to investigate specific issues.
Running Your First Deliverability Test
Most email deliverability testing tools follow a similar process that takes about five minutes.
First, visit the testing tool's website and look for the test option. Many free tools let you start testing immediately without creating an account.
Second, the tool provides you with a unique email address. Copy this address exactly as shown.
Third, send an email from your normal sending system to that test address. Use your actual email template, subject line, and sending setup - not a simplified test version. You want to see how your real campaigns perform.
Fourth, wait for the results. Most tools provide instant or near-instant analysis, though some comprehensive tests might take a few minutes to complete.
Fifth, review the detailed report. Look for red flags in your authentication setup, content analysis, and overall deliverability score.
MXToolbox provides free and paid options to check DNS records, SPF/DKIM setup, and blacklist status by sending an email to a designated address, making it easy to get started.
Testing Across Multiple Email Providers
Your deliverability can vary significantly between different email service providers.
Gmail, Outlook, Yahoo, and other providers each use their own filtering algorithms and reputation systems. An email that performs well with Gmail users might struggle to reach Outlook inboxes.
Testing across providers reveals these discrepancies. Many deliverability tools include multi-provider testing that shows your inbox placement rate for each major email service.
Pay special attention to the providers your audience actually uses. If most of your subscribers use Gmail, prioritize fixing Gmail deliverability issues first.
Run these multi-provider tests regularly, not just once. Deliverability can change over time as your sending patterns evolve and provider algorithms update.
Checking Your DNS Records and Authentication
Your DNS records control your email authentication setup, so verifying these configurations is critical.
Start by checking your SPF record. This TXT record in your DNS should list all mail servers authorized to send emails from your domain. You can use tools like MXToolbox to look up and validate your SPF record.
Next, verify your DKIM signature. Your email platform should provide a DKIM public key that you add to your DNS as a TXT record. Check that this record exists and contains the correct key.
Then, confirm your DMARC policy. This record tells receiving servers what to do when SPF or DKIM checks fail. A properly configured DMARC record also provides valuable reporting about authentication issues.
Don't forget to check your MX records and reverse DNS setup. These aren't directly related to authentication but they impact overall deliverability.
If you're not comfortable making DNS changes yourself, work with your IT team or hosting provider. Getting these settings wrong can break your email delivery completely.
Understanding Your Deliverability Test Results
Your deliverability report contains important insights, but understanding what the numbers actually mean makes all the difference.
Let's break down how to interpret your results and prioritize which issues to fix first.
Interpreting Your Spam Score
Your spam score predicts how likely spam filters are to flag your emails.
Most tools use a scale where lower scores are better. A spam score below 5 is generally safe, while scores above 5 indicate problems that need attention.
The report typically highlights specific elements contributing to your score. Common culprits include suspicious links, promotional language, poor authentication, or content formatting issues.
Focus on the highest-impact factors first. Fixing a major authentication problem will improve your score more than tweaking individual words in your content.
Don't obsess over achieving a perfect zero spam score. That's often unnecessary and might mean your emails are too bland to engage recipients effectively.
Analyzing Inbox vs Spam Folder Placement
Inbox placement rate shows the percentage of your emails that actually reach recipients' primary inboxes.
This metric is more valuable than just knowing whether emails were delivered. An email sitting in a spam folder technically "delivered" but it's not going to generate opens or clicks.
Quality deliverability tools test your inbox placement across multiple providers and show you exactly where your messages land. You might see results like "90% inbox for Gmail, 70% inbox for Outlook, 85% inbox for Yahoo."
Inbox placement rates below 90% indicate deliverability problems that deserve immediate attention. The gap between delivered emails and inbox placement represents lost opportunities.
Track this metric over time rather than focusing on a single test. Trends matter more than individual data points.
Evaluating Authentication Results
Your authentication status report shows whether SPF, DKIM, and DMARC checks passed or failed.
A passing SPF check means your sending server is authorized to send emails from your domain. If this fails, you need to update your SPF record to include your current mail server.
A passing DKIM check confirms your digital signature is valid and your email wasn't tampered with during transmission. Failed DKIM usually means your DKIM record is missing, incorrect, or your email platform isn't properly signing messages.
DMARC results show whether your policy is properly configured and enforced. This is the most complex of the three protocols but also increasingly important for maintaining good deliverability.
Don't ignore authentication failures. Major email providers increasingly rely on these protocols to filter messages, and failed authentication almost guarantees poor inbox placement.
Reviewing Blacklist Status
Blacklist checks show whether your sending IP address or domain appears on any spam databases.
Being listed on a major blacklist can devastate your deliverability overnight. Email providers reference these blacklists when deciding whether to accept your messages.
Different blacklists have different criteria and delisting processes. Some blacklists automatically remove you after a period of good behavior, while others require you to request removal manually.
If you discover you're blacklisted, don't panic. First, identify why you were listed (this information is usually available on the blacklist's website). Fix the underlying problem before requesting delisting, or you'll just end up blacklisted again.
Monitor blacklist status regularly, not just when you notice deliverability problems. Catching a blacklist listing early makes resolution much easier.
SPF, DKIM, and DMARC: Essential Authentication Protocols
Email authentication protocols verify your identity as a legitimate sender.
Regularly authenticating your domain with SPF, DKIM, and DMARC is a foundational best practice for maintaining good email deliverability. Let's break down what each protocol does and how to implement them.
Setting Up SPF Records
SPF (Sender Policy Framework) specifies which mail servers can send emails from your domain.
Setting up SPF requires adding a TXT record to your domain's DNS settings. This record lists the IP addresses or mail servers authorized to send on your behalf.
A basic SPF record looks like this: "v=spf1 include:_spf.google.com ~all". This example authorizes Google's servers to send emails from your domain.
If you use multiple email services (like your email platform plus a transactional email service), you need to include all of them in your SPF record. Each service should provide the specific include statement to add.
Common mistakes include creating multiple SPF records (you can only have one) or exceeding the 10 DNS lookup limit. If you need to authorize many services, consider using SPF flattening tools.
Test your SPF record after implementation using tools like MXToolbox to confirm it's properly formatted and working correctly.
Configuring DKIM Signatures
DKIM (DomainKeys Identified Mail) adds a digital signature to your outgoing emails.
This signature proves the email came from your domain and hasn't been altered during transit. Receiving servers verify this signature using a public key you publish in your DNS.
Setting up DKIM involves two steps. First, your email platform generates a private/public key pair. Second, you add the public key to your DNS as a TXT record.
Your email service provider should give you the exact DNS record to add. It typically looks like "your-selector._domainkey.yourdomain.com" with a long value containing your public key.
The selector (the "your-selector" part) lets you rotate keys or use different keys for different services. Use the selector name your email platform provides.
After adding the DKIM record, send yourself a test email and check the message headers to confirm the signature is present and valid.
Implementing DMARC Policies
DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF and DKIM.
This protocol tells receiving servers what to do when authentication checks fail. It also provides reporting so you can monitor authentication issues affecting your domain.
Start with a monitoring-only DMARC policy that doesn't affect email delivery. A basic monitoring record looks like "v=DMARC1; p=none; rua=mailto:your-email@yourdomain.com".
The "p=none" policy means "don't take action on failed authentication, just report it." This lets you see what's happening before implementing stricter policies.
After monitoring for a few weeks, you can strengthen your policy to "p=quarantine" (send failures to spam) or "p=reject" (block failures entirely).
The reports DMARC generates show you which messages are passing or failing authentication. These reports help you identify unauthorized senders using your domain and fix legitimate authentication issues.
Common Email Deliverability Problems and Solutions
Most deliverability issues fall into a few common categories that you can fix with the right approach.
Let's tackle the problems we see most often and exactly how to resolve them.
Fixing High Bounce Rates
High bounce rates damage your sender reputation quickly and indicate list quality problems.
Hard bounces happen when emails are sent to addresses that don't exist. These should be immediately removed from your list since they'll bounce every time.
Soft bounces occur when temporary issues prevent delivery (like a full inbox or server problems). Monitor soft bounces and remove addresses that consistently soft bounce over multiple campaigns.
The solution is proactive email verification before sending campaigns. Cleaning your list removes invalid addresses before they can bounce and hurt your reputation.
At mailfloss, we automatically check every email address in your database daily. Our system connects directly with platforms like Mailchimp, ActiveCampaign, Klaviyo, and 32 other email service providers.
Once connected (which takes about 60 seconds), mailfloss runs in the background catching invalid addresses, fixing typos, and keeping your bounce rate low without any manual work.
Resolving Authentication Failures
Failed SPF, DKIM, or DMARC checks tell receiving servers not to trust your emails.
Start by identifying which authentication check is failing. Your deliverability test results should clearly indicate whether SPF, DKIM, or DMARC is the problem.
For SPF failures, verify that your SPF record includes all mail servers sending on your behalf. Common culprits include forgotten third-party services or recently added email tools.
For DKIM failures, confirm your DKIM record exists in DNS and contains the correct public key. Also check that your email platform is properly signing outgoing messages.
For DMARC issues, ensure your policy is properly configured and that your SPF and DKIM are aligned (meaning the "from" domain matches the authenticated domain).
After making DNS changes, remember that propagation can take up to 48 hours. Test again after waiting for changes to take effect.
Improving Content to Avoid Spam Filters
Content-based spam filtering catches emails with suspicious characteristics or known spam patterns.
Review your subject lines first. Avoid all caps, excessive punctuation, and words commonly associated with spam (like "free," "urgent," or "act now").
Balance your text-to-image ratio. Emails with mostly images and little text trigger spam filters because spammers use this technique to hide spam content from filters.
Check your links carefully. Shortened URLs, links to suspicious domains, or too many links can all increase your spam score. Use full URLs from reputable domains when possible.
Provide a clear, functional unsubscribe link. This is legally required in most jurisdictions and also helps you maintain better list hygiene.
Test your content with spam analysis tools before sending campaigns. These tools highlight specific problems so you can fix them proactively.
Getting Off Email Blacklists
Blacklist removal requires fixing the problem that caused the listing, then requesting delisting.
First, identify which blacklist you're on and why. Visit the blacklist's website (usually shown in your deliverability test results) and look up your IP address or domain.
Second, fix the underlying issue. Common causes include sending to spam traps, high bounce rates, spam complaints, or security compromises. You can't get delisted without addressing the root problem.
Third, follow the blacklist's specific delisting process. Some blacklists automatically remove you after a period of good behavior. Others require you to submit a delisting request.
Fourth, monitor your status after delisting. Getting blacklisted again will make future delisting much harder.
Prevent future blacklisting by maintaining good list hygiene, monitoring engagement, and following email marketing best practices.
Monitoring and Maintaining Email Deliverability
Email deliverability isn't a one-time fix, it requires ongoing monitoring and maintenance.
We've found that consistent attention to list health prevents most deliverability problems before they impact your campaigns.
Creating a Regular Testing Schedule
Schedule deliverability tests at regular intervals to catch problems early.
Run a basic deliverability check weekly if you send high volumes. This frequent testing helps you spot negative trends before they cause serious damage.
Perform comprehensive multi-provider tests monthly. These deeper tests show how your emails perform across Gmail, Outlook, Yahoo, and other major platforms.
Conduct detailed authentication and DNS checks quarterly. These technical elements rarely change, so less frequent testing is sufficient.
Test immediately after making significant changes to your email infrastructure, template design, or sending patterns. Changes can impact deliverability in unexpected ways.
Document your test results over time. Tracking trends reveals patterns that help you understand what improves or harms your deliverability.
Implementing Automated List Cleaning
Automated email verification keeps your list clean without requiring constant manual attention.
The best approach verifies new addresses as they join your list and regularly re-verifies existing subscribers. This catches addresses that become invalid over time.
At mailfloss, our automated system handles both. We verify addresses when they're added to your list and continuously re-check your entire database for changes.
The automation runs quietly in the background through direct integrations with platforms like HubSpot, Constant Contact, and Drip. You don't need to remember to run reports or manually upload CSV files.
Set up rules for how to handle different types of problem addresses. You might automatically unsubscribe invalid addresses, tag risky ones for review, or update custom fields with verification status.
Our typo-fixing feature automatically corrects common mistakes like "gmal.com" to "gmail.com" before they cause bounces. This happens in real-time without any action needed from you.
Tracking Key Deliverability Metrics
Monitor specific metrics that indicate deliverability health.
Your deliverability rate shows the percentage of emails accepted by receiving servers. Track this separately from inbox placement rate, which shows how many actually reach inboxes.
Bounce rate measures emails that couldn't be delivered. Keep this below 3% to maintain good sender reputation.
Your spam complaint rate indicates how often recipients mark your emails as spam. Even a small increase here can damage your reputation significantly.
Open rates and click rates, while not direct deliverability metrics, reflect engagement levels that influence your sender reputation.
Blacklist status should be checked regularly to catch listings before they impact large portions of your audience.
Create a simple dashboard tracking these metrics over time. This makes it easy to spot problems and measure improvement.
Advanced Strategies for Better Inbox Placement
Once you've mastered the basics, these advanced techniques can push your inbox placement rates even higher.
Segmenting Based on Engagement
Sending patterns affect sender reputation, so adjusting your approach based on subscriber engagement makes sense.
Identify your most engaged subscribers (those who regularly open and click your emails). Send to this group more frequently since their positive engagement strengthens your reputation.
Create separate segments for moderately engaged and rarely engaged subscribers. Reduce sending frequency for less engaged contacts to avoid spam complaints.
Consider re-engagement campaigns for inactive subscribers before removing them entirely. This gives them one last chance to show interest.
Remove chronically inactive subscribers who haven't engaged in six months or more. They hurt your engagement metrics and sender reputation.
This segmentation approach improves overall engagement rates, which signals to email providers that recipients value your messages.
Optimizing Send Times and Frequency
When and how often you send impacts both engagement and deliverability.
Test different send times to find when your audience is most likely to engage. Higher engagement immediately after sending improves how email providers treat your future messages.
Avoid sudden spikes in sending volume. Gradually increase your sending as your list grows rather than jumping from 1,000 emails per day to 50,000.
Maintain consistent sending patterns. Email providers get suspicious when accounts that normally send weekly suddenly send daily.
Don't over-mail your list. Too many emails lead to unsubscribes and spam complaints, both of which damage sender reputation.
Monitor engagement by send frequency to find the sweet spot where recipients stay interested without feeling overwhelmed.
Building Sender Reputation Through Engagement
Email providers reward senders whose recipients actually want to receive their messages.
Focus on getting subscribers to explicitly engage with your emails. Opens, clicks, replies, and moving emails to priority folders all send positive signals.
Ask engaged subscribers to add you to their address book or whitelist your domain. This prevents your future emails from being filtered.
Create email content that encourages replies. Email providers treat two-way conversations more favorably than one-way broadcasts.
Monitor which types of content generate the highest engagement. Double down on content styles that resonate with your audience.
Track engagement metrics by email service provider. If Gmail users engage more than Outlook users, investigate why and adjust your approach.
Take Control of Your Email Deliverability Today
You now know exactly how to check your email deliverability and fix the most common problems.
Start by running a complete deliverability test today. Use a tool like MXToolbox or GlockApps to get baseline measurements of your current inbox placement rate.
Then tackle authentication first. Verify that your SPF, DKIM, and DMARC records are properly configured since these form the foundation of good deliverability.
Next, implement automated list cleaning to keep invalid addresses from damaging your sender reputation. At mailfloss, we make this simple with one-time 60-second setup and automatic daily verification.
Finally, schedule regular testing and monitoring so you catch problems before they impact your marketing results.
Your emails deserve to reach inboxes. Take the first step today and see exactly where you stand.
Want to learn more about improving your overall email deliverability? Check out our complete guide to email deliverability for detailed strategies.
If your emails are landing in spam folders, our guide on why emails go to spam reveals the specific reasons and solutions.
And for marketers specifically, our email deliverability guide for marketers shows how deliverability impacts your campaigns and revenue.