DNS-Only vs. SMTP Verification Modes

Mailthentic supports two verification modes. Understanding the difference helps you choose the right level of verification for your needs.

DNS-Only Mode

DNS-only verification checks everything except the mailbox itself:

• Syntax validation
• Domain existence
• MX record lookup
• SPF, DKIM, and DMARC record checks
• Disposable domain detection
• Role-based address detection

Result: You'll know whether the domain is properly configured to receive email, but not whether the specific mailbox exists.

Best for: Quick domain-level checks, pre-screening large lists before deeper verification, or when SMTP probing isn't needed.

SMTP Mode (Full Verification)

SMTP mode includes everything in DNS-only mode, plus:

• SMTP connection to the mail server
• Mailbox existence check (RCPT TO command)
• Catch-all detection
• Greylisting retry handling
• Provider-specific intelligence

Result: The most accurate verification possible, with a confidence score reflecting the actual mailbox status.

Best for: Pre-send list cleaning, real-time signup validation, and any scenario where you need high confidence.

How the Mode Is Determined

By default, Mailthentic uses SMTP mode for all verifications. DNS-only mode may be used as a fallback when:

• The SMTP worker is temporarily unavailable.
• The domain's mail server is unreachable or times out.
• Your account or the system is configured for DNS-only mode.

Your results will always show which mode was used (verification_mode_used) so you know the depth of each check.