final int numOfThreads = 4;
final SmtpAsyncClient smtpClient = new SmtpAsyncClient(numOfThreads);

// Use SSL?
final boolean enableSsl = true;

// This example defines a connection to smtp.example.com through port 465 over SSL
final SmtpAsyncSessionData sessionData = SmtpAsyncSessionData.newBuilder("smtp.example.com", 465, enableSsl)
        .setSessionContext("client007") // optional parameter used as an ID for debugging purposes
        .setSniNames(null) // optional list of SNI names
        .setLocalAddress(null); // optional local address if present
        .build();

// Session configurations such as timeouts
final SmtpAsyncSessionConfig sessionConfig = new SmtpAsyncSessionConfig()
        .setConnectionTimeout(5000)
        .setReadTimeout(7000);

// Asynchronous call to create a Future containing the session data
final Future<SmtpAsyncCreateSessionResponse> sessionFuture = smtpClient.createSession(
    sessionData, sessionConfig, SmtpAsyncSession.DebugMode.DEBUG_OFF
);

// Check if future is done using the isDone method (non-blocking)
if (sessionFuture.isDone()) {
    System.out.println("Future is ready, can access data without blocking");
} else {
    System.out.println("Future is not done yet");
}

// Gets the session data from the future. This operation will block only if future is not yet complete
final SmtpAsyncCreateSessionResponse sessionResponse = sessionFuture.get();

// The actual session that can be used to issue commands
final SmtpAsyncSession session = sessionResponse.getSession();

// Issue an "EHLO" command asynchronously
final Future<SmtpAsyncResponse> ehloResponseFuture = session.execute(
    new ExtendedHelloCommand("my_domain")
);

try {
    // Get the response, this may block for at most 5 seconds if not completed already
    final SmtpAsyncResponse ehloResponse = ehloResponseFuture.get(5, TimeUnit.SECONDS);
    final Collection<SmtpResponse> responsesLines = ehloResponse.getResponseLines();

    // Access responses
    for (final SmtpResponse response : responsesLines) {
        System.out.println("Raw response: " + response.toString());
        System.out.println("Reply code: " + response.getCode());
        System.out.println("Message: " + response.getMessage());
    }
} catch (TimeoutException e) {
    System.err.println("future did not finish in time");
}

session.close();
smtpClient.shutdown();