verify-email

You will be given one or more email addresses (comma-separated). For each email address, run the verification pipeline below. Report results in a summary table at the end.

Step 1: Syntax check

Verify the email matches a valid format: one @, valid local part (no leading/trailing dots, no consecutive dots), and a valid domain (valid hostname characters, at least one dot).

If the syntax is invalid, mark the email as Invalid (bad syntax) and skip remaining steps.

Step 2: DNS/MX record check

Run dig +short <domain> MX via Bash. Inspect the results:

• If no MX records are returned, try dig +short <domain> A as a fallback (some domains accept mail on their A record).
• If neither returns results, mark as Invalid (no mail server) and skip remaining steps.
• If MX records exist, note the lowest-preference (primary) MX server for Step 4.

Step 3: Disposable email check

Check whether the domain is a known disposable/temporary email provider. Search the web for "is a disposable email" or check against well-known disposable domains (mailinator.com, guerrillamail.com, tempmail.com, throwaway.email, yopmail.com, sharklasers.com, 10minutemail.com, trashmail.com, etc.).

If disposable, flag it as Warning: disposable email provider but continue to Step 4.

Step 4: SMTP RCPT TO verification

This step connects to the mail server and asks if the mailbox exists without sending an email.

Run this Bash script, substituting the email and MX server:

{
  exec 3<>/dev/tcp/<mx_server>/25
  timeout=5

  # Read greeting
  read -t $timeout -u 3 greeting
  echo "GREETING: $greeting"

  # HELO
  echo -e "HELO verify.local\r" >&3
  read -t $timeout -u 3 helo_resp
  echo "HELO: $helo_resp"

  # MAIL FROM
  echo -e "MAIL FROM:<[email protected]>\r" >&3
  read -t $timeout -u 3 mail_resp
  echo "MAIL FROM: $mail_resp"

  # RCPT TO - the actual verification
  echo -e "RCPT TO:<EMAIL_ADDRESS>\r" >&3
  read -t $timeout -u 3 rcpt_resp
  echo "RCPT TO: $rcpt_resp"

  # QUIT
  echo -e "QUIT\r" >&3

  exec 3<&-
  exec 3>&-
} 2>&1