(Java) Office365 POP3 with Client Credentials

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Demonstrates how to interact with the Office365 POP3 server using OAuth2 client credentials. This example uses a new feature available starting in Chilkat v9.5.0.97, which is to provide the client ID, client secret, and tenant ID to Chilkat, and internally Chilkat will fetch OAuth2 access token via client credentials as necessary. Therefore, it is no longer necessary for the application to explicitly fetch the OAuth2 access token beforehand.

Note: This requires the Azure Entra ID application to be configured for client credentials as detailed in this guide: Office365 App Setup for SMTP, POP, IMAP OAuth2 Client Credentials

Note: This example requires Chilkat v9.5.0.97 or greater.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    boolean success;

    // ----------------------------------------------------------------------------------------
    // Important:
    // Your Azure Entra ID app must be explicitly setup to allow for the OAuth2 client credentials flow.
    // Please follow the detailed guide for how to do it here:
    // Office365 App Setup for SMTP, POP, IMAP OAuth2 Client Credentials
    // 
    // Note: Your registered App must have the SMTP.SendAsApp permission.
    // ----------------------------------------------------------------------------------------

    CkJsonObject json = new CkJsonObject();

    // Use your App's actual client ID here:
    json.UpdateString("client_id","2871da2c-8176-4b7f-869b-2311aa82e743");

    // Use your App's actual client secret here:
    json.UpdateString("client_secret","2hu9Q~r5QuryUcEkNbg1btLtnfU1VUXzhSCG6brH");

    // Use this specific scope.
    json.UpdateString("scope","https://outlook.office365.com/.default");

    // Replace the tenant ID part of the URL with your tenant ID.
    json.UpdateString("token_endpoint","https://login.microsoftonline.com/114d7ed6-71bf-4dbe-a866-748364121bf2/oauth2/v2.0/token");

    CkMailMan mailman = new CkMailMan();

    mailman.put_MailHost("outlook.office365.com");
    mailman.put_MailPort(995);
    mailman.put_PopSsl(true);

    // Use your O365 email address here.
    mailman.put_PopUsername("OFFICE365_EMAIL_ADDRESS");

    // When using OAuth2 authentication, leave the password empty.
    mailman.put_PopPassword("");

    // Here is where we use a new feature introduced in Chilkat v9.5.0.97
    // Instead of providing a previously fetched OAuth2 access token, we instead provide the information (above)
    // required for Chilkat to automatically fetch the access token via client credentials.
    mailman.put_OAuth2AccessToken(json.emit());

    // Make the TLS connection to the outlook.office365.com POP3 server.
    success = mailman.Pop3Connect();
    if (success != true) {
        System.out.println(mailman.lastErrorText());
        return;
        }

    // Authenticate using XOAUTH2
    success = mailman.Pop3Authenticate();
    if (success != true) {
        System.out.println(mailman.lastErrorText());
        return;
        }

    // Find out how many emails are on the server..
    int numEmails = mailman.CheckMail();
    if (numEmails < 0) {
        System.out.println(mailman.lastErrorText());
        return;
        }

    // Examine the POP3 session log:
    System.out.println(mailman.pop3SessionLog());

    // The POP3 session log will look something like this:

    // **** Connected to outlook.office365.com:995
    // < +OK The Microsoft Exchange POP3 service is ready. [QwBIADIAUABSADEAOABD...YwBvAG0A]
    // > AUTH XOAUTH2
    // < + 
    // > <base64 string in XOAUTH2 format>
    // < +OK User successfully authenticated.
    // > STAT
    // < +OK 3 375302

    // End the POP3 session and close the connection to the GMail server.
    success = mailman.Pop3EndSession();
    if (success != true) {
        System.out.println(mailman.lastErrorText());
        return;
        }

    System.out.println("Finished.");
  }
}