Cold Email Deliverability Tools: Which Ones Actually Help

By Puzzle Inbox Team · Apr 10, 2026 · 10 min read

Deliverability tools ranked by category. Spam checkers, inbox placement, blacklist monitors, DNS checkers. What's worth paying for and what's free.

Most Deliverability Tools Are Overpriced

The cold email deliverability tool market has bloated. Every vendor claims their tool will fix your inbox placement. Reality: a handful of tools actually help, most of what's needed is free, and the paid tools worth buying have very specific use cases.

Here's the category-by-category breakdown of what actually helps versus what's marketing fluff.

Spam Checkers (Test If Copy Triggers Filters)

Spam checkers analyze your email copy against known spam filter patterns. Good for catching red flags before you send to a real list.

Puzzle Inbox Free Spam Checker

Price: Free.

What it does: Paste copy, get a score and list of specific issues. Checks subject line, body text, link count, word choices, HTML issues.

Worth it: Yes. No cost, immediate feedback, covers the basics.

Mail-tester.com

Price: Free (3 tests per day), $7 per month for more.

Send a test email to a generated address, get a score out of 10. Catches SPF/DKIM/DMARC issues plus content flags.

Worth it: Yes, the free tier covers most needs. Best for catching authentication problems.

Litmus Spam Testing

Price: Starts at $99 per month.

Tests against major spam filters (Barracuda, Spamhaus, etc.). Enterprise-grade.

Worth it: Only for enterprise teams. Overkill for cold email. Most cold email teams don't need the paid feature set.

Inbox Placement Testing (Verify Emails Actually Reach Inbox)

Inbox placement tools send test emails to a network of seed accounts across Gmail, Outlook, Yahoo, etc. You see what percentage land in inbox vs spam vs promotions.

GlockApps

Price: $79 to $149 per month.

Sends tests from your inbox to 50+ seed accounts across major providers. Reports inbox placement percentage, spam placement, missing, and provider-specific breakdown.

Worth it: Yes for ops teams that need data on inbox placement trends. A single test isn't very useful (small sample). Monthly tests across your inbox pool give reliable trend data.

Folderly

Price: $90 per inbox per month.

Combines inbox placement testing with warmup. Priced per inbox, so scales poorly.

Worth it: Rarely. The per-inbox pricing gets expensive fast. Most ops get better value from GlockApps for testing and a separate warmup tool.

InboxAlly

Price: $149 per month.

Heavy on warmup integration. Some reports of aggressive tactics (mass inbox seed activity that looks automated).

Worth it: No. Pricing is in GlockApps territory but the warmup-focused positioning hasn't translated to better cold email deliverability in user reports.

Blacklist Monitoring (Check If Domains Are Flagged)

Blacklists are databases of domains/IPs known for spam. If your domain lands on Spamhaus, Barracuda, or SORBS, your deliverability craters immediately.

MxToolbox Blacklist Check

Price: Free for single lookups, paid monitoring starts at $129 per year.

Check any domain or IP against 100+ blacklists. Free tier is useful for spot checks.

Worth it: Free tier is essential. Paid monitoring only if you're managing 50+ domains and need automated alerts.

Puzzle Inbox Free Blacklist Checker

Price: Free.

Quick blacklist lookup for any domain. Covers the major blacklists.

Worth it: Yes. Free, fast, gets the job done for periodic checks.

HetrixTools

Price: Free tier available, paid from $5 per month for monitoring.

Continuous blacklist monitoring with alerts.

Worth it: Yes for teams managing 10+ domains. Cheap and reliable.

DNS Checkers (Verify SPF, DKIM, DMARC)

DNS tools verify your authentication records are configured correctly. Broken SPF or DKIM means your emails fail authentication and land in spam.

Puzzle Inbox Free DNS Checker

Price: Free.

Check SPF, DKIM, DMARC, and MX records for any domain. Fast and accurate.

Worth it: Yes. Free, no account required, covers what you need.

MxToolbox SuperTool

Price: Free for most lookups.

Industry standard DNS lookup tool. SPF, DKIM, DMARC, MX, blacklist, domain health, etc.

Worth it: Yes. The free tier is one of the most useful tools in cold email operations.

DMARC Analyzer Tools (dmarcian, Valimail, etc.)

Price: Varies, typically $100+ per month.

Process DMARC reports to show you who's sending from your domain and whether authentication is passing.

Worth it: Only if you're managing DMARC reports at scale (enterprise email programs). Overkill for cold email.

Google Postmaster Tools

Price: Free.

Google's official tool for tracking your domain's reputation at Gmail. Shows spam rate, domain reputation, IP reputation, and authentication success rate.

Worth it: Absolutely yes. This is the single most important free deliverability tool for cold email. If you're not checking Postmaster Tools weekly, you're flying blind on your Gmail reputation.

Setup

Verify your sending domain in Postmaster Tools. Data populates after you cross the threshold of daily sending volume (usually 100+ emails per day per domain). Once populated, you see spam rate and reputation trends.

What's Worth Paying For

• GlockApps or equivalent ($79 to $149 per month) if you need inbox placement trend data. Optional, not required.
• HetrixTools ($5+ per month) if you're monitoring 10+ domains and want automated blacklist alerts.
• Email verification (ZeroBounce, NeverBounce, MillionVerifier) priced per lookup. Always worth the spend, prevents the #1 deliverability killer (bounces).

What You Don't Need to Pay For

• Spam checking: free tools cover it.
• Basic DNS lookups: free tools cover it.
• Single blacklist checks: free tools cover it.
• Postmaster Tools data: Google provides it free.
• Most enterprise "deliverability platforms": marketing fluff at cold email scale.

The Real Drivers of Deliverability

Tools don't fix deliverability. Infrastructure does. Tools help you measure and diagnose, they don't solve underlying problems.

The actual drivers of deliverability: quality of your inbox provisioning (pre-warmed vs unwarmed), DNS authentication done correctly, volume per inbox (under 12 for Google), list quality (verified), copy quality (plain text, under 100 words, no links in email 1), and sending patterns (staggered, consistent, Tue/Wed/Thu mornings).

Fix those with good infrastructure and good practices. Then use free tools to monitor. Pay for tools only when they replace manual work you can't keep up with.

Minimum Viable Deliverability Stack

• Email verification (paid per lookup, $0.004 to $0.008 per email)
• Puzzle Inbox free spam checker
• Puzzle Inbox free DNS checker
• Puzzle Inbox free blacklist checker
• Google Postmaster Tools
• MxToolbox free DNS tools

Total cost: only email verification is paid. Everything else is free. This stack covers 90% of what a cold email operation needs for deliverability monitoring.