7 Email Deliverability Testing Tools Worth Using
From free spam-score checkers to full inbox placement tests — what each tool actually measures, and when to use it.
"Deliverability testing" covers several different checks that get conflated: authentication validation, spam-content scoring, inbox placement, and blocklist status. Each needs a different tool. Running the wrong one gives false confidence.
The four things you're actually testing
| Test type | What it checks | When to run it |
|---|---|---|
| Authentication | SPF, DKIM, DMARC records resolve correctly | Once per domain, after DNS changes |
| Spam content scoring | Whether copy/formatting trips spam filter heuristics | Before sending a new template at scale |
| Inbox placement | Whether a real send lands in inbox, promotions, or spam | Periodically, especially after volume increases |
| Blocklist status | Whether your domain/IP appears on DNSBLs | When replies drop suddenly |
The tools
1. MXToolbox
The default first stop. Checks SPF, DKIM, DMARC syntax, MX records, and blocklist status across dozens of DNSBLs in one query. Free, fast, and the most commonly cited tool in deliverability troubleshooting threads for a reason.
2. Google Postmaster Tools
If a meaningful share of your list is Gmail, this is non-negotiable. It shows domain reputation (as Google sees it), spam rate, and delivery errors — data no third-party tool can replicate because it comes directly from Gmail's own signals.
3. Mail-Tester
Send a test email to a generated address and get a spam score out of 10 with a breakdown of what's dragging it down — missing authentication, spammy phrasing, image-to-text ratio, blocklist hits. Best used right before sending a new template to a real list.
4. GlockApps
Actual inbox placement testing across dozens of real mailbox providers (Gmail, Outlook, Yahoo, etc.), showing exactly which land in inbox vs. spam vs. missing entirely. Paid, but it's the closest thing to ground truth for placement.
5. MXToolbox DMARC / DKIM lookup tools
Separate from the general MXToolbox check — these dig into individual record syntax when something's misconfigured and you need to see exactly which tag is wrong.
6. Sender Score (Validity)
IP-level reputation score out of 100, based on spam trap hits, complaint rates, and blocklist history. More relevant for dedicated IP senders than shared-IP platform users.
7. A warmup tool's own deliverability dashboard
Platforms running active warmup — including AlienMail — track spam-folder placement rate as part of the daily warmup cycle, since the warmup network itself is sending and checking placement continuously. This gives an ongoing read rather than a one-time snapshot, which matters more than any single test.
How to actually use these together
- Set up SPF/DKIM/DMARC, then verify with MXToolbox once.
- Before any new template goes out at volume, run it through Mail-Test to catch content issues.
- Connect Google Postmaster Tools if you're sending meaningful Gmail volume — it's free and it's the ground truth for the largest mailbox provider.
- If replies suddenly drop, check blocklist status first — it's the most common silent killer.
- Keep ongoing placement visibility through your warmup tool rather than relying on periodic manual checks.
The bottom line
No single tool tests deliverability — it's a stack of checks for different failure modes. Authentication and blocklist checks are the cheap, fast wins to rule out immediately; inbox placement testing is the one that tells you what's actually happening for real recipients.
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