title: Avoid writing the password of a Gmail account in my code
body: <p>I want to use a Gmail email to work as an SMTP server.</p>
  
  <p>I don't want to write the password for the email server in my code, is  possible another alternative?</p>
  
  <p>Besides, my customer doesn't want to tell me the password of his Gmail email.</p>
  
  <p>So what should I do to use the Gmail email as a SMTP server in my case?</p>