Delphi ActiveX

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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var
success: Integer;
email: TChilkatEmail;

begin
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.

email := TChilkatEmail.Create(Self);

success := email.LoadEml('qa_data/eml/signed.eml');
if (success = 0) then
  begin
    Memo1.Lines.Add(email.LastErrorText);
    Exit;
  end;

if (email.ReceivedSigned = 1) then
  begin
    Memo1.Lines.Add('This email was received with a digital signature.');
    if (email.SignaturesValid = 1) then
      begin
        Memo1.Lines.Add('All signatures are valid.');
      end
    else
      begin
        Memo1.Lines.Add('One or more signatures are NOT valid.');
      end;
  end
else
  begin
    Memo1.Lines.Add('This email was not signed.');
  end;

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