In my case, I have succeded by using your first transport config. I've just included the port to the properties and set it to 587. As mentioned by Google in this link: Send email from a printer, scanner, or app

So here is my transport config:

MailerModule.forRoot({
  transport: {
    service: 'gmail',
    port: 587, 
    secure: false,
    auth: {
      user: process.env.MAILDEV_INCOMING_USER,
      pass: process.env.MAILDEV_INCOMING_PASS,
    },
  },
  defaults: {
    from: '"No Reply" <no-reply@localhost>',
  },
  preview: false,
  template: {
    dir: __dirname + '/templates',
    adapter: new PugAdapter(),
    options: {
      strict: true,
    },
  },
}),

Even though there is an error warning log after the build, like this:

But the module is running successfully: