(Delphi ActiveX) Auto-Refresh O365 Access Token when Sending Email

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Demonstrates how to automatically recover from an expired access token when sending email from smtp.office365.com using OAuth2 authentication. If the server responds with an error indicating that the access token is expired, then we refresh the access token and retry.

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
jsonToken: TChilkatJsonObject;
success: Integer;
mailman: TChilkatMailMan;
email: TChilkatEmail;
oauth2: TChilkatOAuth2;
sbJson: TChilkatStringBuilder;

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

// An Office365 OAuth2 access token must first be obtained prior
// to running this code.

// First get our previously obtained OAuth2 access token.
jsonToken := TChilkatJsonObject.Create(Self);
success := jsonToken.LoadFile('qa_data/tokens/office365.json');

mailman := TChilkatMailMan.Create(Self);

mailman.SmtpHost := 'smtp.office365.com';
mailman.SmtpPort := 587;
mailman.StartTLS := 1;

// Use your Office365 email address for the SmtpUsername.
mailman.SmtpUsername := 'OFFICE365_EMAIL_ADDRESS';
mailman.OAuth2AccessToken := jsonToken.StringOf('access_token');

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

email.Subject := 'This is a test';
email.Body := 'This is a test';
email.From := 'MY_NAME <OFFICE365_EMAIL_ADDRESS>';
success := email.AddTo('John Doe','somebody@example.com');

// Call SendEmail to connect to the SMTP server and send.
// The connection (i.e. session) to the SMTP server remains
// open so that subsequent SendEmail calls may use the
// same connection.  
success := mailman.SendEmail(email.ControlInterface);
if (success = 1) then
  begin
    Memo1.Lines.Add('Mail Sent!');
    Exit;
  end;

// If we fall through to here, it means something failed.
// If we failed because of an invalid or expired access token, we should get this SMTP status code and error message:
//    response: 535 5.7.3 Authentication unsuccessful [CH2PR19CA0023.namprd19.prod.outlook.com]
//    status code: 535
if (mailman.LastSmtpStatus <> 535) then
  begin
    Memo1.Lines.Add(mailman.LastErrorText);
    Exit;
  end;

// If we get here, it means the SMTP status code equaled 535, which is an authentication failure.
// Let's refresh the access token, and then retry..

oauth2 := TChilkatOAuth2.Create(Self);

// Update to use your token endpoint.
// In the Azure Portal, in "App registrations", go to "Endpoints" (located to the right of the "+ New registration" link.)
//    Find your endpoint for the "OAuth 2.0 token endpoint (v2)"
//    See Office365 OAuth2 Endpoints

oauth2.TokenEndpoint := 'https://login.microsoftonline.com/xxxxxxxxxx-71bf-4ebe-a866-738364321bf2/oauth2/v2.0/token';

// Replace these with actual values.
oauth2.ClientId := 'CLIENT_ID';
oauth2.ClientSecret := 'CLIENT_SECRET';

// Get the "refresh_token"
oauth2.RefreshToken := jsonToken.StringOf('refresh_token');

// Send the HTTP POST to refresh the access token..
success := oauth2.RefreshAccessToken();
if (success <> 1) then
  begin
    Memo1.Lines.Add(oauth2.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('New access token: ' + oauth2.AccessToken);
Memo1.Lines.Add('New refresh token: ' + oauth2.RefreshToken);

// Update the JSON with the new tokens.
jsonToken.UpdateString('access_token',oauth2.AccessToken);
jsonToken.UpdateString('refresh_token',oauth2.RefreshToken);

// Save the new JSON access token response to a file.
sbJson := TChilkatStringBuilder.Create(Self);
jsonToken.EmitCompact := 0;
jsonToken.EmitSb(sbJson.ControlInterface);
sbJson.WriteFile('qa_data/tokens/office365.json','utf-8',0);

Memo1.Lines.Add('OAuth2 authorization granted!');
Memo1.Lines.Add('New Access Token = ' + oauth2.AccessToken);

// -------------------------------------------------
// Retry the SMTP send using the refreshed access token.

Memo1.Lines.Add('Retrying the send using the refreshed access token.');

mailman.OAuth2AccessToken := oauth2.AccessToken;

success := mailman.SendEmail(email.ControlInterface);
if (success = 0) 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('Email sent!');
end;