Frequently Asked Questions

General

Does Mailthentic send actual emails to verify addresses?

No. Mailthentic uses the SMTP protocol to communicate with mail servers, but it never sends an actual email message. The process stops after asking the server whether the recipient exists (RCPT TO command). No message body or subject line is ever transmitted.

Will the person know their email was verified?

No. Email verification is invisible to the recipient. No email lands in their inbox, and there are no notifications or logs on their end.

Is email verification legal?

Email verification — checking whether an address is technically valid and deliverable — is a standard industry practice and is legal in all major jurisdictions. It does not involve accessing anyone's account or reading their messages. However, always ensure your email marketing practices comply with applicable laws (CAN-SPAM, GDPR, etc.).

How accurate is Mailthentic?

Accuracy depends on the email provider and domain configuration. For providers that give definitive responses (Yahoo, ProtonMail, most custom domains), accuracy is very high. For providers like Google Workspace and Microsoft 365 that accept all recipients, we provide the highest confidence possible given the provider's limitations.

Credits & Pricing

Do credits expire?

Credit expiration policies depend on your account type. Check the Credits page in your dashboard for details on your specific credits.

Can I get a refund for unused credits?

Please contact our support team for refund inquiries. We handle these on a case-by-case basis.

Am I charged for duplicate emails in bulk uploads?

No. Duplicates are automatically detected and removed before processing. You're only charged for unique addresses.

Am I charged for invalid results?

Yes. Each verification consumes 1 credit regardless of the result. Verification resources (DNS lookups, SMTP connections) are consumed even when the result is "invalid."

Technical

What file formats does bulk verification support?

Currently, CSV (.csv) files are supported. Email addresses must be in the first column.

Is there a limit on bulk file size?

There is no hard row limit, but processing time scales with list size. For very large lists (100K+), consider splitting them into multiple files.

Why does Google Workspace always show "unconfirmed"?

Google Workspace mail servers accept all RCPT TO commands with a 250 response, regardless of whether the mailbox exists. This is by design from Google to prevent email enumeration. Mailthentic detects this and marks the result as "deliverable_unconfirmed" rather than falsely claiming the mailbox is confirmed.

What happens if the SMTP worker is down?

If the SMTP verification worker is unavailable, Mailthentic automatically falls back to DNS-only verification mode. Your results will show verification_mode_used: "dns_only" and the confidence scores will reflect the reduced depth of verification.

Can I use Mailthentic for real-time signup verification?

Yes. Use the single verification feature in your signup flow. The verification typically completes within a few seconds, making it suitable for real-time validation.