Sending an email without opening the third party app such as Gmail etc in Flutter

EmailSender.dart

import 'package:mailer/mailer.dart';
import 'package:mailer/smtp_server.dart';

main() async {
  String username = '[email protected]';
  String password = 'password';
  
  final smtpServer = gmail(username, password);
  // Use the SmtpServer class to configure an SMTP server:
  // final smtpServer = SmtpServer('smtp.domain.com');
  // See the named arguments of SmtpServer for further configuration
  // options.  

  // Create our message.
  final message = Message()
    ..from = Address(username, 'Your name')
    ..recipients.add('[email protected]')
    ..ccRecipients.addAll(['[email protected]', '[email protected]'])
    ..bccRecipients.add(Address('[email protected]'))
    ..subject = 'Test Dart Mailer library :: 😀 :: ${DateTime.now()}'
    ..text = 'This is the plain text.\nThis is line 2 of the text part.'
    ..html = "<h1>Test</h1>\n<p>Hey! Here's some HTML content</p>";

  try {
    final sendReport = await send(message, smtpServer);
    print('Message sent: ' + sendReport.toString());
  } on MailerException catch (e) {
    print('Message not sent.');
    for (var p in e.problems) {
      print('Problem: ${p.code}: ${p.msg}');
    }
  }
  // DONE


  // Let's send another message using a slightly different syntax:
  //
  // Addresses without a name part can be set directly.
  // For instance `..recipients.add('[email protected]')`
  // If you want to display a name part you have to create an
  // Address object: `new Address('[email protected]', 'Display name part')`
  // Creating and adding an Address object without a name part
  // `new Address('[email protected]')` is equivalent to
  // adding the mail address as `String`.
  final equivalentMessage = Message()
    ..from = Address(username, 'Your name 😀')
    ..recipients.add(Address('[email protected]'))
    ..ccRecipients.addAll([Address('[email protected]'), '[email protected]'])
    ..bccRecipients.add('[email protected]')
    ..subject = 'Test Dart Mailer library :: 😀 :: ${DateTime.now()}'
    ..text = 'This is the plain text.\nThis is line 2 of the text part.'
    ..html = '<h1>Test</h1>\n<p>Hey! Here is some HTML content</p><img src="cid:[email protected]"/>'
    ..attachments = [
      FileAttachment(File('exploits_of_a_mom.png'))
        ..location = Location.inline
        ..cid = '<[email protected]>'
    ];

  final sendReport2 = await send(equivalentMessage, smtpServer);

  // Sending multiple messages with the same connection
  //
  // Create a smtp client that will persist the connection
  var connection = PersistentConnection(smtpServer);

  // Send the first message
  await connection.send(message);

  // send the equivalent message
  await connection.send(equivalentMessage);

  // close the connection
  await connection.close();
}