(Delphi DLL) 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 non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
http: HCkHttp;
cert: HCkCert;
success: Boolean;
iss: PWideChar;
scope: PWideChar;
oauth_sub: PWideChar;
numSec: Integer;
accessToken: PWideChar;
mailman: HCkMailMan;
email: HCkEmail;

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

http := CkHttp_Create();

// --------------------------------------------------------------------------------
// 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 := CkCert_Create();
success := CkCert_LoadPfxFile(cert,'c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12','notasecret');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    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 := CkHttp__g_SvcOauthAccessToken(http,iss,scope,oauth_sub,numSec,cert);
if (CkHttp_getLastMethodSuccess(http) <> True) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    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 := CkMailMan_Create();

// Set the properties for the GMail SMTP server:
CkMailMan_putSmtpHost(mailman,'smtp.gmail.com');
CkMailMan_putSmtpPort(mailman,587);
CkMailMan_putStartTLS(mailman,True);

CkMailMan_putSmtpUsername(mailman,'bob@yourcompany.com');
CkMailMan_putOAuth2AccessToken(mailman,accessToken);

// Create a new email object
email := CkEmail_Create();

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

success := CkMailMan_SendEmail(mailman,email);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkMailMan__lastErrorText(mailman));
    Exit;
  end;

success := CkMailMan_CloseSmtpConnection(mailman);
if (success <> True) 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.');

CkHttp_Dispose(http);
CkCert_Dispose(cert);
CkMailMan_Dispose(mailman);
CkEmail_Dispose(email);

end;