Sending an SMTP email in Dart

There's a library called mailer, which does exactly what you asked for: sends out emails.

Set it as a dependency in your pubspec.yaml and run pub install:

dependencies:
  mailer: any

I will give a simple example using Gmail on my local Windows machine:

import 'package:mailer/mailer.dart';

main() {
  var options = new GmailSmtpOptions()
    ..username = '[email protected]'
    ..password = 'my gmail password'; // If you use Google app-specific passwords, use one of those.

  // As pointed by Justin in the comments, be careful what you store in the source code.
  // Be extra careful what you check into a public repository.
  // I'm merely giving the simplest example here.

  // Right now only SMTP transport method is supported.
  var transport = new SmtpTransport(options);

  // Create the envelope to send.
  var envelope = new Envelope()
    ..from = '[email protected]'
    ..fromName = 'Your company'
    ..recipients = ['[email protected]', '[email protected]']
    ..subject = 'Your subject'
    ..text = 'Here goes your body message';

  // Finally, send it!
  transport.send(envelope)
    .then((_) => print('email sent!'))
    .catchError((e) => print('Error: $e'));
}

The GmailSmtpOptions is just a helper class. If you want to use a local SMTP server:

var options = new SmtpOptions()
  ..hostName = 'localhost'
  ..port = 25;

You can check here for all possible fields in the SmtpOptions class.

Here's an example using the popular Rackspace Mailgun:

var options = new SmtpOptions()
  ..hostName = 'smtp.mailgun.org'
  ..port = 465
  ..username = '[email protected]'
  ..password = 'from mailgun';

The library supports HTML emails and attachments as well. Check out the example to learn how to do that.

I am personally using mailer with Mailgun in production use.