Free email deliverability tools
Check whether an address is real, audit a domain’s SPF, DKIM, DMARC and MX records, or work out what cleaning a list will cost. All free, no account and no credit card — they run the same engine the paid product does, so you can judge the accuracy before paying for anything.
Email checker
Is this one address real?
A live SMTP mailbox check on a single address, with catch-all and disposable detection. Five checks a minute.
List health check
What is wrong with this list before I verify it?
Drop a CSV of up to 5,000 rows: duplicates, bad syntax, typo domains, disposable, role and dead domains. Runs in your browser.
Deliverability audit
Can this domain send and receive mail?
MX, SPF, DKIM, DMARC and blocklist status for any domain, with what each result means for mail sent to or from it.
Disposable checker
Is this address temporary?
Instant lookup against thousands of known throwaway providers. No rate limit — it is a list lookup, not a network call.
Cost calculator
What will cleaning this list actually cost?
Cost per 1,000 addresses across subscription and pay-as-you-go vendors, including against the plan you are on now.
Check one record at a time
The full audit runs all of these together. These pages cover each record on its own, with what the result means and how to fix it.
MX record lookup
An MX lookup returns the mail servers that accept email for a domain, each with a priority number where lower is tried first.
SPF record checker
An SPF check reads the domain's SPF TXT record and reports which servers it authorises to send mail and what should happen to everything else.
DMARC record checker
A DMARC check reads the TXT record at `_dmarc.yourdomain.com` and reports the policy it publishes: none, quarantine or reject.
DKIM record checker
A DKIM check looks for the public keys a domain publishes in DNS.
Email blacklist check
A blacklist check queries the major public blocklists to see whether a domain is listed.
Build the records, not just check them
Both run entirely in your browser — nothing is sent anywhere. The SPF builder counts DNS lookups as you add providers, which is what actually breaks SPF.
Why these are free
A DNS lookup and a short SMTP conversation cost nothing per query. There is no per-check fee for us to recover, so charging for a single check would be a pricing decision rather than a cost. The tools are rate-limited per IP because port 25 connections are a shared resource, not because they are expensive.
The paid product is the bulk version of the same engine: CSV uploads to 100,000 rows, the email finder, website enrichment and cached repeat verification, for $29.99 a month. See what is included.
Reference
- SMTP error codes — what 550, 421 and 552 mean when a send fails, and what to do about each.
- Deliverability glossary — catch-all, spam traps, greylisting, authentication records and the rest.
- Disposable domain list — all 8,740 throwaway providers we block, with a page on each major one.