Persist Verifiable SMTP Delivery Status for Sent Emails

mailbox.org should persist verifiable SMTP delivery status evidence for every sent email.

For each outbound message, the sent-mail record should include the final SMTP transaction result, e.g. 250 OK or the exact error response, with timestamp, recipient domain/MX, message ID, envelope recipient, TLS status, and retry/failure history.

A read receipt is not sufficient. If the recipient does not confirm it, the sender still needs independent evidence that the recipient’s mail server accepted the message.

Use case: In legal, regulatory, and GDPR proceedings, customers may need court-usable evidence of server-side acceptance by the recipient’s mail server. If an employee later cannot find the message in their mail client, that is an internal issue for the recipient’s compliance/IT function to investigate. The sender must still be able to prove that the recipient’s mail infrastructure accepted the email.

A tamper-evident export/PDF for each sent message would be sufficient.