Check if an Email Was Received Digitally Signed

See more Email Object Examples

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.

Chilkat C# Downloads

Download Chilkat for C#

bool success = false;

//  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.

Chilkat.Email email = new Chilkat.Email();

success = email.LoadEml("qa_data/eml/signed.eml");
if (success == false) {
    Debug.WriteLine(email.LastErrorText);
    return;
}

if (email.ReceivedSigned == true) {
    Debug.WriteLine("This email was received with a digital signature.");
    if (email.SignaturesValid == true) {
        Debug.WriteLine("All signatures are valid.");
    }
    else {
        Debug.WriteLine("One or more signatures are NOT valid.");
    }

}
else {
    Debug.WriteLine("This email was not signed.");
}

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