Email Verifier

This is a local cold email verification tool. Drag in a CSV and it will:

• Validate each email live (MX, SMTP, syntax)
• Show real-time progress per file
• Let you cancel jobs mid-run
• Persist your results even after refresh
• Let you download the verified leads when ready

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🧱 Setup

1. Clone the repo:

git clone [repo-link]

2. Open the Folder

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⚙️ Install Dependencies

Open Terminal, then run:

cd "/Users/yourname/Desktop/Email Verifier"
python3 -m venv venv
source venv/bin/activate
pip install flask flask-cors dnspython email-validator

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🚀 Run the App

Terminal Tab 1:

source venv/bin/activate
python3 verify-app.py

You should see one of:

[SMTP OK] Port 25 is reachable - live mailbox verification is active.

[SMTP BLOCKED] Port 25 is blocked on this network - running in offline mode.
  Results will use 'unknown' + a confidence score instead of a false 'valid'.

Terminal Tab 2:

cd "/Users/yourname/Desktop/Email Verifier"
python3 -m http.server 3000

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🌐 Use the Tool

Open in your browser:

http://localhost:3000/index.html

• Drag in one or more CSVs
• Each file shows a progress bar, live email log, cancel button, and close (X)
• When done, a download link will appear
• Everything persists across refreshes

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⚙️ Configuration (optional)

Copy verifier_config.example.json to verifier_config.json to override any default. All fields are optional; unset ones use the defaults below.

• helo_hostname — the domain the verifier identifies itself as on SMTP (HELO/EHLO + MAIL FROM). Defaults to this machine's hostname. The verifier never sends an actual email (it disconnects right after the RCPT check, before the DATA stage), so setting this to a domain you own is safe for that domain's sending reputation — only the probing IP address accumulates any reputation signal, not the domain.
• max_workers (15) — concurrent verification threads.
• per_domain_max_concurrent (2) / per_domain_delay_s (1.0) — throttles how hard any single mail server gets hit, to avoid rate-limit blocks.
• catchall_probe_count (2) — random addresses probed per domain to detect catch-all (accept-everything) domains.
• enable_second_pass (true) / greylist_retry_delay_s (90) — greylisted/rate-limited addresses are automatically re-checked after this delay, recovering mailboxes a single pass would miss.
• enable_gravatar (true) — best-effort free Gravatar existence check, used only to refine confidence on ambiguous (catch-all/unknown) results.

Result columns

Each row in the output CSV gets: status (valid/invalid/risky/unknown), reason, confidence (0-100), is_role, is_disposable, is_free, is_catch_all, did_you_mean (typo suggestion), mx_host, provider, smtp_message, has_spf, has_dmarc, has_gravatar, reliable.

unknown means the mailbox could not be confirmed either way (SMTP unreachable, blocked, or still ambiguous after retry) — treat it as "needs review," not as invalid. risky means the domain accepts all mail (catch-all) or is a provider known to accept-then-bounce (e.g. Yahoo/AOL), so a 250 response there isn't trustworthy on its own.

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