8 Best Email Deliverability Tools (Free and Paid)

Email Deliverability Tools Compared

Email deliverability tools test, monitor, and explain whether your emails reach the inbox. No single tool covers every part of that, so most senders combine 2 or 3.

Each tool answers a different question:

• Spam checkers: Why might this message get filtered?
• Inbox placement tools: Where did it land at each provider?
• Blocklist monitors: Is my domain or IP listed anywhere?
• DMARC monitors: Who’s sending email as my domain?
• Mailbox provider dashboards: How does Gmail or Outlook see me?

Here’s how the 10 tools compare.

Tool	Job	Free option	Paid from
Email Detective	Spam and authentication check	Free, no signup	N/A
Mail-Tester	Spam and authentication check	Occasional tests, no account	$5 for 10 tests
GlockApps	Inbox placement testing	2 spam test credits	$59/month
MailReach	Inbox placement and warm-up	3 free spam tests per 24 hours	$19.50 per mailbox/month
MxToolbox	Blocklist monitoring	Weekly checks, 1 domain	$129/month
Postmark DMARC Digests	DMARC monitoring	Weekly digest	$14/month per domain
Google Postmaster Tools	Gmail sender data	Free	N/A
Microsoft SNDS	Outlook IP data	Free	N/A

How I Picked These Tools

I picked these tools for people who send transactional emails. That means receipts, sign-up confirmations, and password resets.

That rules out most cold-outreach platforms. They bundle warm-up with sales features you won’t use.

Each tool had to meet 3 criteria:

• It does one deliverability job well and says what that job is.
• It has a free tier, a free test, or a trial.
• It works with any email service, not just one provider’s platform.

I left out email builders, rendering previews, and list-cleaning tools. They’re useful, but they solve a different problem.

Spam and Authentication Checkers

A spam and authentication checker tells you why one message might get filtered. You send a real email to a test address. The tool then scores what the receiving server saw.

Here’s how to read the results:

• Authentication fails first. A failed SPF, DKIM, or DMARC check outweighs everything else. Fix it before you touch your content.
• SpamAssassin scores add up. Each rule that fires adds points. SpamAssassin’s default spam threshold is 5 points, so lower is better.
• Content notes are hints. A spammy subject line rarely sinks a well-authenticated email on its own.

These checkers inspect one message at a time. They don’t tell you where it landed in Gmail or Outlook. That’s what inbox placement tools do, and I cover them in the next section.

1. Email Detective by SendLayer

Email Detective is a free deliverability checker from SendLayer. One thing I like about it is that it doesn’t require you to sign up for an account to use the tool.

You open Email Detective and get a one-time email address. Then you’ll need to send a message to it from the app you want to test.

The report covers 4 areas:

• Authentication: SPF, DKIM, and DMARC results for your message.
• Blacklists: Every public blocklist it queried, and what each one returned.
• Spam filtering: A SpamAssassin score, with the rules that fired.
• Content: A written review of your message, subject line, and wording.

The report also lists your subject line, HELO name, and sending IP. Basic scores show right away. To unlock the full report, you’ll need to enter an email address.

Email Detective deletes reports and messages 30 days after the message arrives. The link in your report email works for the same 30 days.

WordPress users can run it using the WP Mail SMTP plugin. To do so, go to WP Mail SMTP » Tools » Email Detective.

Then enter the email address you’d like to receive the detailed report on and click Run a Deliverability Test.

The plugin then sends a real email through your site’s configured mailer. It’s free in both the Lite and Pro versions.

Pricing: Free.

Pros:

• No account needed for the basic scores
• Explains each failed check in plain language
• Tests the exact mail path your site or app uses

Cons:

• Doesn’t measure inbox placement across Gmail, Outlook, and Yahoo
• One message per test, so it won’t spot trends over time

Best for: Website owners and developers who want a quick, free diagnosis.

2. Mail-Tester

Mail-Tester is a long-running spam checker that works the same way. You send an email to a unique address, then open your score.

It also links to separate SPF, DKIM, and DMARC helper tools on the same site. You can run occasional manual tests without an account.

Running the same message through 2 checkers is a cheap sanity check. If both flag the same rule, you know where to start.

Pricing: Paid credits start at $5 for 10 tests. Monthly plans start at $10 for 50 tests.

Pros:

• Familiar and quick to use
• Pay-as-you-go credits if you test often

Cons:

• Mail-Tester doesn’t state the free allowance on its pricing page
• Like any checker, it scores one message, not placement

Best for: Anyone who wants a second opinion on a single test email.

Inbox Placement and Seed-List Testing Tools

Inbox placement tools show where your email actually lands. They send your message to seed inboxes at many providers. Then they report inbox, spam, or missing for each one.

This shows results by provider without asking real recipients. It costs more than a spam check. Most senders run it before a launch or after a sudden drop.

3. GlockApps

GlockApps is a dedicated inbox placement tester. Its tests report placement across major mailbox providers, alongside spam filter results.

It also processes DMARC reports, so one account covers placement and DMARC data.

Pricing: The free plan includes 2 spam test credits and 10,000 DMARC messages. Paid plans start at $59/month for 360 test credits.

Pros:

• Free credits let you try a real placement test
• DMARC monitoring included

Cons:

• 2 free tests don’t go far
• Paid plans cost more than most site owners need

Best for: Teams who want placement data before a big send.

4. MailReach

MailReach combines spam tests with inbox placement by provider. It’s mainly a warm-up tool, but you can buy test credits on their own.

Its test reports include an SPF, DKIM, and DMARC check and a blocklist check.

Pricing: MailReach’s free spam checker allows up to 3 tests per 24 hours. Its warm-up plan costs $19.50 per mailbox per month and includes 20 test credits.

Pros:

• Placement results by provider
• Slack or webhook alerts on automatic tests

Cons:

• No ongoing free plan beyond 3 free tests a day
• Built mainly around cold email inboxes

Best for: Senders who also need warm-up for a new mailbox.

Blocklist Monitoring Tools

A blocklist monitor checks your domain and IP against public blocklists on a schedule. It warns you when a blocklist adds you, so you can act before mail bounces.

Spamhaus runs several major public blocklists. You can check your IP or domain for free on its site.

If a list adds you, the fix happens at the list operator. Find out why the list added you, fix the cause, then follow that list’s removal steps.

5. MxToolbox

MxToolbox is a free toolkit for email DNS and blocklist checks. Its lookups cover blacklists, SPF, DKIM, DMARC, and general DNS problems.

The free account adds weekly blocklist monitoring for 1 domain. That’s enough for most small senders.

Pricing: Free for weekly monitoring of 1 domain. Paid plans start at $129/month.

Pros:

• Free lookups need no account
• Weekly alerts on the free plan

Cons:

• Paid plans jump straight to agency pricing
• Weekly checks can miss a short listing

Best for: Every sender, as a free baseline.

DMARC Monitoring Tools

DMARC monitoring tools turn mailbox providers’ XML reports into readable charts. They show who’s sending email as your domain. They also show whether those messages pass SPF and DKIM.

You need this before moving your DMARC policy from p=none to quarantine or reject. Otherwise, you risk blocking a real service you forgot about.

6. Postmark DMARC Digests

Postmark DMARC Digests sends you a plain weekly summary of your DMARC reports. You don’t need to log in to a dashboard.

The free version covers your top 10 mail sources with 7 days of history.

Pricing: Free weekly digest. The paid plan is $14/month per domain, with a 14-day trial.

Pros:

• Free and simple
• Readable without DMARC expertise

Cons:

• The free version has no web dashboard
• Only 7 days of history on the free version

Best for: Small senders who want DMARC data without another dashboard.

Mailbox Provider Dashboards

Mailbox provider dashboards show how a provider itself sees your mail. The data comes straight from Gmail or Outlook, not from a test inbox.

They’re free, but you have to prove you own the domain or IP first. Yahoo runs a similar program called Sender Hub.

7. Google Postmaster Tools

Google Postmaster Tools shows how Gmail treats mail from your domain. It’s free and run by Google.

The dashboard includes compliance status, spam rate, authentication, encryption, and delivery errors. The compliance status dashboard tracks Google’s sender requirements.

To set it up, add your domain and verify it with a DNS TXT record.

Data will start showing once Gmail has enough of your mail to report on.

Pricing: Free.

Pros:

• First-party Gmail data
• Shows whether you meet Google’s sender rules

Cons:

• Low-volume senders may see little data
• Gmail only

Best for: Anyone sending to Gmail addresses, which is most senders.

8. Microsoft SNDS

Microsoft Smart Network Data Services (SNDS) shows data for IPs sending to Outlook.com and Hotmail. It covers each IP that Microsoft lets you view.

You request access to the IPs you’re responsible for. Access expires 10 months after approval.

SNDS access goes to whoever controls the IP. On a shared IP, that’s usually your email service.

Pricing: Free.

Pros:

• First-party Outlook data
• Includes Microsoft’s Junk Email Reporting Program

Cons:

• Works by IP, not domain
• Not useful on shared sending IPs

Best for: Senders who own a dedicated IP.

Sender Requirements and the Tools That Check Them

Gmail, Yahoo, and Outlook now set firm rules for high-volume senders. Here’s which tool confirms you meet each one.

Requirement	Who sets it	Tool that checks it
Pass SPF and DKIM	Google, Yahoo, Microsoft	Email Detective, Mail-Tester, MxToolbox
Publish a DMARC record	Google, Yahoo, Microsoft	Email Detective, EasyDMARC, Postmark DMARC Digests
Keep spam rate under 0.3%	Google	Google Postmaster Tools
Stay off blocklists	Best practice	MxToolbox, Email Detective

Google’s rules took effect in February 2024. They apply to senders of 5,000+ messages a day to Gmail. Google says to keep your spam rate under 0.1% and never reach 0.3%.

Microsoft’s rules started on May 5, 2025, for the same volume to Outlook.com and Hotmail. They require passing SPF and DKIM, plus DMARC at p=none or stricter.

You may send fewer than 5,000 emails a day. Meeting these rules still helps, because they describe what filters already reward.

Which Email Deliverability Tool to Start With

Start with the free tools, and pick based on the symptom you’re seeing. Here’s the order I’d use:

1. Emails land in spam: Run a spam and authentication check with Email Detective or Mail-Tester.
2. Only Gmail users complain: Set up Google Postmaster Tools and check your spam rate.
3. Emails suddenly bounce: Look up your IP and domain in MxToolbox.
4. Someone spoofs your domain: Add DMARC monitoring with Postmark DMARC Digests or EasyDMARC.
5. You’re launching a new domain: Run an inbox placement test with GlockApps first.

Most fixes come back to authentication. If SPF, DKIM, or DMARC fail, fix your DNS records first.

A good email service also does much of this work for you. SendLayer authenticates your domain during setup and handles bounces and suppression automatically.

Frequently Asked Questions

Here are answers to common questions about email deliverability tools.