Send Email with Digital Signature in Delphi - S/MIME with SHA1, SHA256 and SHA512¶

unit Unit1;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, EASendMailObjLib_TLB; // add EASendMail unit
type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

const
  ConnectNormal = 0;
  ConnectSSLAuto = 1;
  ConnectSTARTTLS = 2;
  ConnectDirectSSL = 3;
  ConnectTryTLS = 4;

  CRYPT_MACHINE_KEYSET = 32;
  CRYPT_USER_KEYSET = 4096;
  CERT_SYSTEM_STORE_CURRENT_USER = 65536;
  CERT_SYSTEM_STORE_LOCAL_MACHINE = 131072;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  oSmtp : TMail;
begin
  oSmtp := TMail.Create(Application);
  oSmtp.LicenseCode := 'TryIt';

  // Set your sender email address
  oSmtp.FromAddr := 'test@emailarchitect.net';
  // Add recipient email address
  oSmtp.AddRecipientEx('support@emailarchitect.net', 0);

  // Set email subject
  oSmtp.Subject := 'test email from Delphi with digital signature';
  // Set body text
  oSmtp.BodyText := 'this is a test email sent from Delphi with digital signature';

  // Add digital signature
  if not oSmtp.SignerCert.FindSubject('test@emailarchitect.net',
    CERT_SYSTEM_STORE_CURRENT_USER, 'my') then
    begin
      ShowMessage(oSmtp.SignerCert.GetLastError());
      exit;
    end;
  if not oSmtp.SignerCert.HasCertificate Then
    begin
      ShowMessage('Signer certificate has no private key, ' +
      'this certificate can not be used to sign email');
    end;

  // Your SMTP server address
  oSmtp.ServerAddr := 'smtp.emailarchitect.net';

  // User and password for ESMTP authentication, if your server doesn't require
  // user authentication, please remove the following codes
  oSmtp.UserName := 'test@emailarchitect.net';
  oSmtp.Password := 'testpassword';

  // ConnectTryTLS means if server supports SSL/TLS connection, SSL/TLS is used automatically
  oSmtp.ConnectType := ConnectTryTLS;

  // If your server uses 587 port
  // oSmtp.ServerPort := 587;

  // If your server uses 25/587/465 port with SSL/TLS
  // oSmtp.ConnectType := ConnectSSLAuto;
  // oSmtp.ServerPort := 587; // 25 or 587 or 465

  ShowMessage('start to send email ...');
  if oSmtp.SendMail() = 0 then
    ShowMessage('email was sent successfully!')
  else
    ShowMessage('failed to send email with the following error: '
    + oSmtp.GetLastErrDescription());

end;

end.