Email verifier for B2B leads
A lead list is only as good as the emails on it. LeadMind checks every email before you send: whether the address is well formed, whether the domain has a working mail server, whether it is disposable or catch-all, and whether the mailbox itself exists. No email is ever sent.
What we check
- Syntax — a real address with a real public domain ending (international domains included).
- Mail server — the domain’s MX records, the fallback to its own address when there is no MX, and domains that publish a “null MX” to say they accept no mail at all.
- Disposable domains — an open list of about 9,000 throwaway-inbox providers, refreshed from the public disposable-email-domains project.
- Role addresses — shared inboxes such as info@ or sales@ are flagged, not penalised: for a local business they are often the right contact.
- Free providers and typos — Gmail, Outlook and similar are flagged, and a likely typo such as gmial.com comes back with a suggestion.
- Mailbox check — a dedicated verification server asks the receiving mail server whether the mailbox exists, then disconnects before any message is sent.
What the statuses mean
| Status | Meaning | Typical reasons |
|---|---|---|
deliverable | The receiving mail server confirmed the mailbox exists. | SMTP mailbox check accepted the address |
undeliverable | Mail to this address cannot arrive. | Bad syntax, no mail server, null MX, mailbox rejected |
risky | Mail may be accepted, but that proves nothing about the mailbox. | Catch-all domain, disposable (throwaway) domain |
unknown | The evidence was not conclusive. | Only the domain could be checked, server blocked or deferred the check |
Every result also carries a reason code and the individual checks (syntax, mx, disposable, role, freeProvider, smtp), so you can decide for yourself whether to send to a role address or a free-provider mailbox.
Catch-all domains, honestly
Some mail servers accept every address, real or not. A catch-all domain answers “yes” to any mailbox, so no verifier can confirm a specific person there. LeadMind marks those addresses risky instead of calling them verified. Large providers such as Yahoo and AOL behave the same way and come back unknown.
Ask for verified emails in the prompt
Add “with verified email” to any request — “40 dental clinics in Dubai with verified email”. Leads whose email cannot be confirmed are dropped before delivery and never charged. Emails guessed from a company’s naming pattern are labelled guessed, and a guess that bounces is removed rather than delivered.
Email verifier MCP for Claude, ChatGPT and Gemini
LeadMind's MCP server includes an email verifier tool, verify_emails. Connect it once and your assistant can check up to 25 addresses per call: “verify these emails before I send the campaign”. It answers with the status, the reason and a typo suggestion for each address, and the same connector also finds the leads. For whole lists, the same connector has the bulk tools below.
- Claude: Settings → Connectors → Add custom connector, then paste the MCP URL from the setup guide and sign in.
- ChatGPT: Settings → Apps & Connectors → Developer mode → Create, with the same URL and OAuth.
- Gemini CLI: add the URL to
~/.gemini/settings.jsonand run/mcp auth leadmind.
Verify a whole list
For a list longer than 25, start a bulk job. One job takes up to 5,000 addresses, runs in the background and ends with a CSV of every result. Your assistant picks the right tool by the size of the list, so you can just ask:
“Verify these 1,200 emails from my CSV and give me a download link.”
| MCP tool | REST | What it does |
|---|---|---|
verify_emails | POST /v1/verify/emails | Quick check of up to 25 addresses, answered inline. |
start_email_verification | POST /v1/verify/jobs | Starts a bulk job for up to 5,000 addresses and returns its id at once. |
get_email_verification | GET /v1/verify/jobs/:id | Progress and status counts while it runs; a CSV download link when it is done. |
get_verification_quota | GET /v1/verify/quota | Your plan, checks used and left this period, and the reset date. |
Duplicates are removed, and badly formed entries come back undeliverable without a lookup or a quota unit. The whole list is reserved against your quota when the job starts: if it does not fit, the job is refused up front instead of stopping halfway, and any address that was never checked goes back to your quota. Bulk results carry the same four statuses, and an address that cannot be settled stays unknown rather than being guessed dead.
Verify from the API or the dashboard
- REST API —
POST /v1/verify/emailswith{ "emails": [...] }for up to 25,POST /v1/verify/jobsfor a list of up to 5,000 (then page the results or download the CSV), andGET /v1/verify/quotafor what is left this period. - Leads from every job on a paid plan are verified automatically; see
emailStatusandemailSourceon each lead and in the CSV.
Plans and quota
| Plan | Job leads | Standalone checks per billing period |
|---|---|---|
| Free | Email source label only | Not included |
| Starter | Verified automatically | 1,000 |
| Growth | Verified automatically | 5,000 |
| Scale | Verified automatically | 20,000 |
Each distinct valid address counts once, in a quick check or a bulk list; invalid addresses and duplicates in the same call are free. Verification has its own monthly quota and never spends lead credits. Compare plans or create a free account to start.
Privacy
Verification results are cached so repeat checks are fast, but the cache keeps only a SHA-256 hash of each address, never the address itself, for 1 to 30 days depending on how settled the answer is. Bulk job results keep each address encrypted so you can download them, and are deleted 30 days after the job. See the privacy policy.
Frequently asked questions
- Is there an email verifier MCP server?
- Yes. LeadMind's MCP server includes four email verification tools: verify_emails checks up to 25 addresses and answers inline, start_email_verification and get_email_verification verify a whole list of up to 5,000 and return a CSV, and get_verification_quota shows what is left this period. Claude, ChatGPT, Gemini or any MCP client can use them. Connect from the setup guide at /docs/connect; they use the same account, plan and verification quota as the dashboard.
- How many emails can I verify at once?
- Up to 25 addresses per quick check (verify_emails or POST /v1/verify/emails), answered straight away. For a longer list, a bulk job takes up to 5,000 addresses (start_email_verification or POST /v1/verify/jobs), runs in the background and ends with a CSV download. One bulk job runs at a time per account.
- How does LeadMind verify emails?
- Each address goes through a syntax check, a DNS lookup for the mail server (MX, including null MX), a disposable-domain list, role and free-provider detection, a typo check, and then an SMTP mailbox check from a dedicated verification server that asks the receiving mail server whether the mailbox exists.
- Does email verification send an email?
- No. The mailbox check opens a connection to the receiving mail server and asks about the recipient, then disconnects before any message is sent. Nobody receives anything.
- What is a catch-all email domain?
- A domain whose mail server accepts mail for every address, real or not. Because the server says yes to everything, no verifier can confirm a specific mailbox there, so LeadMind marks those addresses risky instead of pretending they are verified.
- Is email verification included in the free plan?
- No. Verification is included in the paid plans: Starter covers 1,000 standalone checks per billing period, Growth 5,000 and Scale 20,000. On the Free plan every lead still shows where its email came from (listing, website or guessed), but not a verification status.
- Do verified leads from a job count against the quota?
- No. On paid plans, emails on the leads a job delivers are verified automatically and do not count. The quota only applies to addresses you check yourself, whether in a quick check of up to 25 or a bulk list of up to 5,000.
- How does a bulk list count against my quota?
- Each distinct valid address counts once; duplicates and badly formed entries are free. The whole list is reserved when the job starts, and a list larger than what is left is refused up front rather than half checked. Addresses that were never checked, because you cancelled or the check failed on our side, go back to your quota. Verification uses its own monthly quota, never your lead credits.
- Can I ask for only leads with verified emails?
- Yes. Add "with verified email" to your prompt, for example "40 dental clinics in Dubai with verified email". Leads whose email cannot be confirmed are dropped and never charged, and guessed emails that bounce are removed.
- Why do some addresses come back unknown?
- Some providers, such as Yahoo and AOL, accept every address, and some servers block or defer checks. When the evidence is not conclusive LeadMind says unknown rather than guessing.
- Does LeadMind store the email addresses it verifies?
- The verification cache keeps only a SHA-256 hash of each address with its result, for 1 to 30 days depending on how settled the answer is, so repeat checks are fast without storing the address itself. Bulk job results keep the address, encrypted, so you can download them; they are deleted 30 days after the job.