deliverability
Email Deliverability Tools: What Each Category Actually Does
Disclosure: this site is operated by the MailPilot team. MailPilot sits in two of the six categories below (warmup and placement monitoring). The category framework is useful regardless of what you end up buying.
People buy the wrong deliverability tool constantly, because “my emails go to spam” is a symptom with at least six different causes — and each cause has its own category of tool. Here is the map.
What are the different types of email deliverability tool?
| Category | Answers the question | Example symptom it explains |
|---|---|---|
| Authentication checkers | Are SPF, DKIM and DMARC correct and aligned? | Mail refused outright, or marked unauthenticated |
| Blacklist monitors | Is my domain or IP on a blocklist? | Sudden total failure to one or many providers |
| Inbox placement testers | Which folder or tab did it land in? | Mail is accepted but nobody replies |
| List verification | Are these addresses real? | High bounce rate, reputation falling |
| Warmup services | Does this mailbox have any sending history? | New domain filtered despite everything being correct |
| Reputation dashboards | What does the provider think of me? | Gradual decline with no obvious cause |
Which deliverability tools are free?
Two of these categories are free and rule out the most common root causes:
- Authentication. A missing DKIM signature or a DMARC policy that does not align will undermine everything else you do. Check SPF, DKIM and DMARC.
- Blacklists. If you are listed, nothing else matters until you are delisted. Check your domain and IP.
Run both before spending anything. A meaningful share of “deliverability problems” are one of these two, and both are free to find.
Why are inbox placement numbers unreliable?
Inbox placement is the category where the numbers are least trustworthy, for a specific technical reason.
When Gmail sorts a message into the Promotions tab, that message still carries the INBOX label. Any tool that checks for INBOX and stops has just recorded a Promotions landing as a clean inbox hit. The recipient’s Primary tab never displayed it.
This is not hypothetical — our own scoring did exactly this until we fixed it in October 2026, and correcting it lowered our reported inbox rates. If a placement tool cannot tell you that it separates CATEGORY_PROMOTIONS from the Primary inbox, treat its inbox rate as an upper bound rather than a measurement.
What do Google Postmaster Tools and Microsoft SNDS tell you?
Google Postmaster Tools gives you Gmail’s own view of your domain reputation, spam complaint rate and authentication success. Microsoft SNDS does the equivalent for Outlook. Both are free, both are first-party, and both are more authoritative about that provider than any third-party estimate. They are also limited: Gmail-only and Outlook-only respectively, domain-level rather than per-mailbox, and they need real volume before they show anything.
How is warmup different from the other tools?
Warmup does not diagnose. It builds the one thing no checker can create: sending history. A brand-new domain with flawless authentication, a clean list and zero blacklist entries will still get filtered, because mailbox providers weight history heavily and a new domain has none. See what email warmup actually is, and the tool comparison if you have decided you need one.
What order should you check things in?
- Check authentication. Free.
- Check blacklists. Free.
- Connect Google Postmaster Tools and Microsoft SNDS. Free.
- Verify your list if bounces are above roughly 2%.
- Only then buy placement monitoring or warmup — and only for the category your symptom actually points at.
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Start free with MailPilotEmail Deliverability Tools — FAQ
What are email deliverability tools?
They are six distinct categories of tool, not one product: authentication checkers that validate SPF, DKIM and DMARC; blacklist monitors that watch whether your domain or IP is listed; inbox placement testers that report which folder or tab your mail landed in; list verification that removes invalid addresses before you send; warmup services that build sending reputation on a new mailbox; and provider reputation dashboards such as Google Postmaster Tools and Microsoft SNDS.
Which email deliverability tool should I use first?
Start with the free ones that diagnose rather than fix. Check SPF, DKIM and DMARC, then check your domain and sending IP against the major blacklists. Both are free and both are common root causes. Only buy a paid tool once you know which category your actual problem is in — otherwise you are guessing with money.
Do I need a deliverability tool if my emails are already landing?
Monitoring is worth it if sending matters to your revenue, because deliverability fails quietly. A domain gets listed, or a provider starts filtering, and the first signal is usually a drop in replies rather than an error. Alerting on reputation and placement means you find out in hours instead of weeks.
Is Google Postmaster Tools enough on its own?
It is essential and free, but it only covers Gmail, only shows data once you send meaningful volume to Gmail, and reports domain-level reputation rather than per-mailbox placement. Pair it with Microsoft SNDS for Outlook, and with per-mailbox placement data if you send from more than a handful of mailboxes.
Can a deliverability tool fix a blacklisted domain?
No tool can delist you. Blacklist monitors tell you that you are listed and on which list; removal means fixing the underlying cause — compromised account, bad list hygiene, spam complaints — and then filing a delisting request with that specific blacklist. A tool shortens the time to discovery, which is where most of the damage happens.