Delphi - Verify digital signature and decrypt email - S/MIME¶

// include EAGetMailObjLib_TLB unit to your Delphi Project
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, EAGetMailObjLib_TLB, StdCtrls;

unit Unit1;

interface

uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, StdCtrls, EAGetMailObjLib_TLB;

type
    TForm1 = class(TForm)
        Button1: TButton;
        procedure Button1Click(Sender: TObject);
    private
        { Private declarations }
        procedure ParseEmail(fileName: WideString);
    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.ParseEmail(fileName: WideString);
Var
    oMail: TMail;
    i: Integer;

    addrs: IAddressCollection;
    addr: IMailAddress;

    atts: IAttachmentCollection;
    att: IAttachment;

    oCert: TCertificate;
    oSignerCert: ICertificate;
begin
    oMail := TMail.Create(Application);
    oMail.LicenseCode := 'TryIt';
    oMail.LoadFile(fileName, false);

    if oMail.IsEncrypted then
        try
            // this email is encrypted, decrypt it by default user certificate
            oMail.ConnectTo(oMail.Decrypt(nil));
            // You can also use specified certificate like this
            // oCert := TCertificate.Create(Application);
            // oCert.LoadFromFile('c:\test.pfx', 'pfxpassword', CRYPT_USER_KEYSET);
            // oMail.Load(oMail.Decrypt(oCert.DefaultInterface).Content);
        except
            on ep: exception do
                ShowMessage('Decrypt Error: ' + ep.Message);
        end;

    if oMail.IsSigned then
        try
            // this email is digital signed, verify signature
            oSignerCert := oMail.VerifySignature();
            ShowMessage('This email contains a valid digital signature.');

            // You can add the certificate to your certificate storage like this
            // oSignerCert.AddToStore(CERT_SYSTEM_STORE_CURRENT_USER,
            // 'addressbook');
            // Then you can use send the encrypted email back to this sender.
        except
            on ep: Exception do
                ShowMessage('Verify signature Error: ' + ep.Message);
        end;

    // Parse email sender
    ShowMessage('From: ' + oMail.From.Address);

    // Parse email to recipients
    addrs := oMail.ToList;
    for i := 0 To addrs.Count - 1 do
    begin
        addr := addrs.Item[i];
        ShowMessage('To: ' + addr.Address);
    End;

    // Parse email cc recipients
    addrs := oMail.CcList;
    for i := 0 To addrs.Count - 1 do
        begin
            addr := addrs.Item[i];
            ShowMessage('Cc: ' + addr.Address);
        end;

    // Parse email subject
    ShowMessage('Subject: ' + oMail.Subject);

    // Parse email text body
    ShowMessage('Text body: ' + oMail.TextBody);

    // Parse email HTML body
    ShowMessage('HTML body: ' + oMail.HtmlBody);

    // Parse attachment
    atts := oMail.AttachmentList;
    for i := 0 To atts.Count - 1 do
        begin
            att := atts.Item[i];
            ShowMessage(att.Name);
        end;

end;

procedure TForm1.Button1Click(Sender: TObject);
begin
    try
        ParseEmail('c:\test folder\test.eml');
    except
        on ep:Exception do
            ShowMessage('Error: ' + ep.Message);
    end;
end;

end.