Vocabularysmtp.
privateInputsOutputsDefinition: email>headers ( email -- assoc )    [        now timestamp>rfc822 "Date" ,,        message-id "Message-Id" ,, "1.0" "MIME-Version" ,,        "base64" "Content-Transfer-Encoding" ,, {            [ from>> "From" ,, ]            [ to>> ", " join "To" ,, ]            [ cc>> ", " join [ "Cc" ,, ] unless-empty ]            [ subject>> "Subject" ,, ]            [ email-content-type "Content-Type" ,, ]        } cleave    ] H{ } make ;