(Delphi ActiveX) OAuth2 for a GMail using a P12 Service Account Key

See more GMail REST API Examples

Note: This example does not work for Personal Google Accounts where the email domain is @gmail.com

For more information, see https://www.chilkatsoft.com/google_workspace_setup_smtp_gmail.asp

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
http: TChilkatHttp;
cert: TChilkatCert;
success: Integer;
iss: WideString;
scope: WideString;
oauth_sub: WideString;
numSec: Integer;
accessToken: WideString;
mailman: TChilkatMailMan;
email: TChilkatEmail;

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

http := TChilkatHttp.Create(Self);

// --------------------------------------------------------------------------------
// For a step-by-step guide for setting up your Google Workspace service account,
// see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
// --------------------------------------------------------------------------------
// Begin by loading your Google service account key (.p12)
cert := TChilkatCert.Create(Self);
success := cert.LoadPfxFile('c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12','notasecret');
if (success <> 1) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

// The ISS is your service account email address ending in gserviceaccount.com.
iss := 'chilkatsvc@chilkat25.iam.gserviceaccount.com';

// The scope is always the following string:
scope := 'https://mail.google.com/';

// The sub is your company email address
oauth_sub := 'bob@yourcompany.com';

// The access token is valid for this number of seconds.
numSec := 3600;

accessToken := http.G_SvcOauthAccessToken(iss,scope,oauth_sub,numSec,cert.ControlInterface);
if (http.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end
else
  begin
    Memo1.Lines.Add('access token: ' + accessToken);
  end;

// The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.

// -----------------------------------------------------------------------
mailman := TChilkatMailMan.Create(Self);

// Set the properties for the GMail SMTP server:
mailman.SmtpHost := 'smtp.gmail.com';
mailman.SmtpPort := 587;
mailman.StartTLS := 1;

mailman.SmtpUsername := 'bob@yourcompany.com';
mailman.OAuth2AccessToken := accessToken;

// Create a new email object
email := TChilkatEmail.Create(Self);

email.Subject := 'This is a test';
email.Body := 'This is a test';
email.From := 'Bob <bob@yourcompany.com>';
success := email.AddTo('Recipient','recipient@example.com');
// To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

success := mailman.SendEmail(email.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(mailman.LastErrorText);
    Exit;
  end;

success := mailman.CloseSmtpConnection();
if (success <> 1) then
  begin
    Memo1.Lines.Add('Connection to SMTP server not closed cleanly.');
  end;

Memo1.Lines.Add('Successfully sent email using Gmail with a service account key.');
end;