Visual Basic 6.0

Check if an Email Was Received Digitally Signed

Demonstrates the read-only Chilkat Email.ReceivedSigned property, which is true if the email was originally received carrying one or more digital signatures. Knowing a message was signed is separate from knowing the signature checked out, so this example also reads SignaturesValid to report whether the signed content verified.

Background: A digital signature on an email (S/MIME) provides two things: authenticity (it was really sent by the holder of a particular certificate) and integrity (the content was not altered in transit). The sender signs a hash of the message with their private key; the recipient verifies it with the sender's public certificate. ReceivedSigned simply tells you a signature is present — verifying it is a separate step exposed through SignaturesValid.

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Visual Basic 6.0

Dim success As Long
success = 0

'  Demonstrates the read-only Email.ReceivedSigned property, which is true if this
'  email was originally received with a digital signature.  Use SignaturesValid to
'  determine whether the signed content actually verified.

Dim email As New ChilkatEmail

success = email.LoadEml("qa_data/eml/signed.eml")
If (success = 0) Then
    Debug.Print email.LastErrorText
    Exit Sub
End If

If (email.ReceivedSigned = 1) Then
    Debug.Print "This email was received with a digital signature."
    If (email.SignaturesValid = 1) Then
        Debug.Print "All signatures are valid."
    Else
        Debug.Print "One or more signatures are NOT valid."
    End If

Else
    Debug.Print "This email was not signed."
End If

'  Note: Paths such as "qa_data/..." are relative local filesystem paths,
'  relative to the current working directory of the running application.