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Email Verifier
Verify email addresses via syntax checking, MX record lookup, and SMTP handshake.
MarkdownPython
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email-verifier/
├── LICENSE
├── README.md
├── examples/
│ └── sample_emails.txt
├── free-sample.zip
├── guide/
│ ├── 01_features.md
│ ├── 02_quick-start.md
│ ├── 03_configuration.md
│ └── 04_faq.md
├── index.html
└── src/
└── email_verifier.py
📖 Documentation Preview README excerpt
Email Verifier
Verify email addresses via three layers of validation: syntax checking, MX record lookup, and SMTP handshake. Catch bad emails before they bounce.
Features
- Syntax validation — RFC 5322-compliant regex with clear error messages
- MX record lookup — DNS-based domain verification using stdlib only
- SMTP handshake — Mailbox existence check without sending an email
- Disposable domain detection — Flags known throwaway email services
- Role address detection — Identifies non-personal addresses (admin@, support@, etc.)
- Batch processing — Verify entire lists from text files or CSVs
- Multiple output formats — JSON, CSV, or plain text
- Rate limiting — Configurable delay between SMTP checks
Requirements
- Python 3.10+
- No external dependencies (stdlib only)
Quick Start
# Verify a single email
python src/email_verifier.py user@example.com
# Verify a list from a file
python src/email_verifier.py --file examples/sample_emails.txt
# Output results to JSON file
python src/email_verifier.py --file examples/sample_emails.txt --output results.json
# Skip SMTP checks (faster, syntax + MX only)
python src/email_verifier.py --file examples/sample_emails.txt --no-smtp
# CSV output format
python src/email_verifier.py --file examples/sample_emails.txt --format csv --output results.csv
Output Format
Each verified email produces a result object:
{
"email": "user@example.com",
"status": "valid",
"syntax_valid": true,
"mx_found": true,
"smtp_connectable": true,
"mailbox_exists": true,
"is_disposable": false,
"is_role_address": false,
"mx_records": ["example.com"],
"smtp_response": "250 OK",
"error": "",
"checked_at": "2026-03-14T12:00:00+00:00"
}
... continues with setup instructions, usage examples, and more.
📄 Code Sample .py preview
src/email_verifier.py
#!/usr/bin/env python3
"""
Email Verifier — Email Arsenal (DataNest)
Verifies email addresses via three layers of validation:
1. Syntax validation (RFC 5322 compliance)
2. MX record lookup (DNS resolution)
3. SMTP handshake (mailbox existence check)
Usage:
python email_verifier.py user@example.com
python email_verifier.py --file emails.txt --output results.json
python email_verifier.py --batch emails.txt --workers 4
Dependencies: Python 3.10+ stdlib only (no pip packages)
License: MIT
"""
from __future__ import annotations
import argparse
import csv
import dns.resolver # NOQA — fallback below if unavailable
import json
import logging
import re
import smtplib
import socket
import struct
import sys
import time
from dataclasses import asdict, dataclass, field
from datetime import datetime, timezone
from enum import Enum
from pathlib import Path
from typing import TextIO
# ---------------------------------------------------------------------------
# Constants
# ---------------------------------------------------------------------------
# RFC 5322 simplified email regex — catches 99% of real-world addresses
# without going full-BNF. Intentionally rejects quoted local parts.
EMAIL_REGEX = re.compile(
r"^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+"
r"@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?"
r"(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$"
)
# Maximum length per RFC 5321
# ... 522 more lines ...