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

In previous section, I introduced how to send email with embedded images. In this section, I will introduce how to sign email with digital certificate in Delphi.

Introduction

S/MIME (Secure/Multipurpose Internet Mail Extensions) is a standard for public key encryption and signing of MIME data.

Digital signature prevents email content is faked or changed in transport level. Encrypting email protects email content from exposure to inappropriate recipients. Both digital signature and email encrypting depend on digital certificate.

If you have an email digital signature certificate installed on your machine, you can find it in “Control Panel” -> “Internet Options” -> “Content” -> “Certificates” -> “Personal”.

Delphi email ceritificate

Then you can use your email certificate to sign the email by the following code. If you don’t have a certificate for your email address, you MUST get a digital certificate for personal email protection from third-party certificate authorities such as www.verisign.com.

If you need a free certificate for your email address, you can go to http://www.comodo.com/home/email-security/free-email-certificate.php to apply for one year free email certificate.

Note

Remarks: All of samples in this section are based on first section: Send email in a simple Delphi project. To compile and run the following example codes successfully, please click here to learn how to create the test project and add reference of EASendMail to your project.

[Delphi - Send email with digital signature (S/MIME) - Example]

The following example codes demonstrate how to send email with digital signature in Delphi.

Note

To get the full sample projects, please refer to Samples section.

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
  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';

  // If your SMTP server requires SSL connection, please add this line
  // oSmtp.SSL_init();

  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.

Signature Algorithm

You can use SignatureHashAlgorithm property to set MD5, SHA1, SHA256, SHA384 or SHA512 signature algorithm. SHA256 is recommended.

Next Section

At next section I will introduce how to encrypt email with digital certificate in Delphi.

Appendix

Comments

If you have any comments or questions about above example codes, please click here to add your comments.