Delphi DLL

Load .eml and Decrypt (smime.p7m)

Loads an encrypted email from a .eml file and decrypts using certificate w/ private key found in a .p12 (or .pfx) file.

The Content-Type and Content-Disposition email headers of the email to be decrypted look similar to this:

Content-Type: application/x-pkcs7-mime; smime-type=enveloped-data;
	name="smime.p7m"
Content-Disposition: attachment; filename="smime.p7m"

Delphi DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
email: HCkEmail;

begin
success := False;

email := CkEmail_Create();

// Add a PFX (or .p12) to be used for decryption
success := CkEmail_AddPfxSourceFile(email,'myCert.p12','passwordForP12');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkEmail__lastErrorText(email));
    Exit;
  end;

// Loading the .eml automatically decrypts.
success := CkEmail_LoadEml(email,'encrypted.eml');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkEmail__lastErrorText(email));
    Exit;
  end;

// The email now exists as it was prior to encryption.
// Your app may access the email's subject, body, attachments,
// etc. using the Chilkat Email API...

// Save the decrypted email:
success := CkEmail_SaveEml(email,'decrypted.eml');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkEmail__lastErrorText(email));
    Exit;
  end;

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

CkEmail_Dispose(email);

end;