(Delphi ActiveX) Add DKIM-Signature Header to MIME / Email

Demonstrates how to add a DKIM-Signature header field to a MIME message.

Note: The DKIM / DomainKey functionality is included with the Chilkat MIME license.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
dkim: TChilkatDkim;
password: WideString;
privKey: TPrivateKey;
success: Integer;
fac: TCkFileAccess;
mimeData: Array of Byte;
dkimSignedMime: Array of Byte;

begin
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Important: It is helpful to send the contents of the
// dkim.LastErrorText property when requesting support.

dkim := TChilkatDkim.Create(Self);

// To create a DKIM signature for email (i.e. MIME),
// you'll need to provide the following:
// (1) An RSA private key in any common file format.
// (2) The domain name (typically the same domain
// as the sender of an email).
// (3) A selector for the domain name -- an arbitrary string
// to identify the matching public key in DNS.

// To allow an email recipient to verify the DKIM signature via an
// external email client supporting DKIM or using other software,
// you will need to create a DNS record with the selector
// and matching public key.  This example does not provide
// information about DKIM DNS record creation.  
// (Chilkat does not provide an API for creating DNS records.  
// Creating the DKIM DNS record is something you would do
// manually.)

// Set the domain and selector:
// You'll need to provide your own values here..
dkim.DkimDomain := 'chilkatsoft.com';
dkim.DkimSelector := 'tuna';

// Load a private key from any common RSA private key
// format, such as DER, PKCS8, PEM, XML, etc.
// The LoadDkimPkFile method automatically detects
// the file format and reads it appropriately.
// If a password is not required, you'll still need to provide
// a password string argument, but it is ignored.
password := 'optionalPassword';
privKey := TPrivateKey.Create(Self);
success := privKey.LoadAnyFormatFile('myPrivateKey.pem',password);
if (success <> 1) then
  begin
    Memo1.Lines.Add(privKey.LastErrorText);
    Exit;
  end;

success := dkim.SetDkimPrivateKey(privKey.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(dkim.LastErrorText);
    Exit;
  end;

// Load a MIME file into a byte array.
fac := TCkFileAccess.Create(Self);

mimeData := fac.ReadEntireFile('testMessage.eml');
if (fac.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(fac.LastErrorText);
    Exit;
  end;

// Sign it.  This adds the DKIM-Signature header and
// returns the new MIME with DKIM-Signature added.

dkimSignedMime := dkim.AddDkimSignature(mimeData);
if (dkim.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(dkim.LastErrorText);
    Exit;
  end;

success := fac.WriteEntireFile('dkimSigned.eml',dkimSignedMime);
if (success <> 1) then
  begin
    Memo1.Lines.Add(fac.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Success.');
end;