How to Test Email Deliverability: A Complete Checklist

Best Practices

You want to know if your emails will reach inboxes before you send an important campaign or notice deliverability dropping. Testing email deliverability means checking multiple components: your authentication setup, your reputation, and where your emails actually land.

This guide walks through a complete testing process, from quick checks you can do right now to deeper investigations for persistent problems.

Test Your Authentication Records

Authentication is the foundation of deliverability. Start here because authentication failures are the most common cause of spam filtering and the easiest to fix.

Check Your SPF Record

Your SPF record declares which servers can send email for your domain. Test your SPF configuration to verify:

• A record exists: If there's no SPF record, that's your first problem
• All senders are included: Your email provider, marketing tools, CRM, transactional service — every service that sends as your domain needs to be listed
• The record is valid: Syntax errors invalidate the entire record
• You're under the lookup limit: SPF allows a maximum of 10 DNS lookups; exceeding this makes your record fail

A healthy SPF check shows a valid record that includes all your sending services and stays within the lookup limit.

Check Your DKIM Setup

DKIM adds cryptographic signatures to your emails. Test your DKIM configuration for each service that sends email:

• The DNS record exists: Each sending service typically uses its own DKIM selector
• The public key is valid: The record should contain a properly formatted key
• Signatures verify: Test emails should pass DKIM verification

Different email services use different selectors. You may need to test multiple selectors if you use multiple services.

Check Your DMARC Policy

DMARC ties SPF and DKIM together and controls what happens when authentication fails. Verify your DMARC configuration to confirm:

• A record exists: No DMARC means you're not controlling authentication failures
• Policy is set: p=none monitors but doesn't protect; p=quarantine or p=reject actively filter unauthenticated email
• Reporting is configured: The rua tag should point to an address where you can receive aggregate reports

If you're just starting with DMARC, p=none is fine while you verify legitimate email passes authentication. Once confirmed, increase to a stronger policy.

Check Your MX Records

While MX records primarily affect incoming email, they're part of your email infrastructure. Verify your MX records are correctly configured — especially important after DNS migrations or domain transfers.

Test Your Reputation

Even with perfect authentication, poor reputation can send your emails to spam. Reputation is harder to test directly, but you can check for obvious problems.

Check for Blacklist Listings

Run a blacklist check on your sending domain and IP addresses. Being listed on major blacklists (Spamhaus, Barracuda, SORBS) significantly affects deliverability.

If you find listings:

1. Identify why you were listed (check the blacklist's website)
2. Fix the underlying problem
3. Submit a removal request following the blacklist's process
4. Monitor to ensure you don't get relisted

Review Your Sending Metrics

Check your email service provider's dashboard for reputation indicators:

• Bounce rate: Should be under 2%. Higher suggests list quality problems.
• Complaint rate: Should be under 0.1%. Higher means recipients are marking you as spam.
• Open rates: Declining rates can indicate inbox placement problems.

Google Postmaster Tools (for Gmail) and Microsoft SNDS (for Outlook) provide additional insight into how those specific providers view your reputation.

Send Test Emails

Testing tools can only tell you so much. Actually sending emails and seeing where they land gives you real-world data.

Create Test Accounts

Set up free email accounts at major providers:

• Gmail (personal and Google Workspace)
• Outlook.com (personal and Microsoft 365)
• Yahoo Mail
• Apple iCloud

These represent the majority of recipients for most senders.

Send Representative Emails

Send test emails that match your actual sending:

• Use your production email service, not a different sending method
• Include the same content structure as real emails (similar length, similar links, similar images)
• Send at similar volume patterns to what you actually do
• Include both transactional-style and marketing-style content if you send both

Check Inbox Placement

For each test email, verify:

• Did it arrive? Check inbox, spam, and promotions/updates tabs
• How long did it take? Delays can indicate filtering
• What do the headers show? Look at authentication results in email headers

To view authentication results in headers:

• Gmail: Open the email → Three dots → Show original
• Outlook.com: Open the email → Three dots → View message source
• Yahoo: Open the email → Three dots → View raw message

Look for spf=pass, dkim=pass, and dmarc=pass in the authentication headers.

Interpret Test Results

Understanding what your test results mean helps you prioritize fixes.

Authentication Failures

If SPF, DKIM, or DMARC fail in email headers:

• SPF fail: Your sending server's IP isn't in your SPF record. Add the correct include or IP.
• DKIM fail: The signature doesn't verify. Check that your DNS record matches your sending service's configuration.
• DMARC fail: Neither SPF nor DKIM passed and aligned. Fix the underlying SPF or DKIM issue.

Authentication failures are fixable with DNS changes. Make the change, wait for propagation, and test again.

Landing in Spam

If authentication passes but email still lands in spam:

• Check blacklist status: Listings can override good authentication
• Review reputation metrics: High complaints or bounces hurt placement
• Examine content: Certain formatting or link patterns may trigger filters
• Consider recipient engagement history: Low engagement with previous emails affects future placement

Landing in Promotions/Updates

Gmail's tabs and Outlook's focused inbox sort email based on content and sender type:

• Marketing content typically goes to Promotions
• Notifications often go to Updates
• This isn't necessarily a problem — many users check these tabs regularly

If you want primary inbox placement, focus on personal, text-based content over formatted marketing templates. But don't obsess over tabs — engagement matters more than which tab an email lands in.

Inconsistent Results Across Providers

Different providers have different filtering logic. If email lands in inbox at Gmail but spam at Outlook:

• Check for provider-specific blacklistings
• Review your reputation specifically with that provider
• Check authentication headers at the problem provider

Provider-specific issues often relate to reputation rather than authentication.

Set Up Ongoing Monitoring

Testing is valuable, but one-time tests don't catch problems that develop later.

What Can Change

• DNS records can be accidentally modified or deleted
• New email services need to be added to SPF
• DKIM keys can expire or be rotated without updating DNS
• Blacklist listings can appear without warning
• Sending reputation can decay over time

What to Monitor

For comprehensive deliverability monitoring, track:

• Authentication records: Daily checks that SPF, DKIM, and DMARC are valid
• Blacklist status: Regular checks against major blacklist databases
• Sending metrics: Bounce rates, complaint rates, engagement
• Inbox placement: Periodic test sends to verify email is arriving

Manual testing catches problems eventually. Automated monitoring catches them when they happen.

A Complete Testing Checklist

Use this checklist when testing your email deliverability:

Authentication

• [ ] SPF record exists and is valid
• [ ] All sending services included in SPF
• [ ] Under 10 DNS lookups in SPF
• [ ] DKIM records exist for each sending service
• [ ] DKIM signatures verify correctly
• [ ] DMARC record exists
• [ ] DMARC policy set to quarantine or reject
• [ ] MX records correctly configured

Reputation

• [ ] Not listed on major blacklists
• [ ] Bounce rate under 2%
• [ ] Complaint rate under 0.1%
• [ ] No sudden drops in engagement metrics

Inbox Placement

• [ ] Test email reaches Gmail inbox
• [ ] Test email reaches Outlook inbox
• [ ] Test email reaches Yahoo inbox
• [ ] Authentication headers show pass for SPF, DKIM, DMARC

Ongoing

• [ ] Monitoring configured for authentication changes
• [ ] Monitoring configured for blacklist listings
• [ ] Regular review of sending metrics scheduled

Stop Worrying About Email Deliverability

The Email Deliverability Suite monitors your SPF, DKIM, DMARC, MX records and blacklist status daily. Get alerts when something breaks — before your emails stop arriving.