title: "STARTTLS is required to send mail" error with git send-email when using an outlook email
body: <p>I'm using ubuntu 20.04 and initially, I did not have <code>git send-email</code> as a valid command. I installed <code>git-email</code> and then <code>git send-email</code> started working.</p>
  <p>I have the following config file:</p>
  <pre><code>[sendemail]
      # smtpuser = &lt;myemail@outlook.com&gt;
      from = My Name &lt;myemail@outlook.com&gt;
      smtpserver = smtp.office365.com
      smtpencryption = STARTTLS
      smtpserverport = 587
  </code></pre>
  <p>When I run <code>git send-email --to &lt;myemail@outlook.com&gt; patches/*.patch</code> to test it and send the respective patches to <em>my</em> email, I get the following output:</p>
  <pre><code>5.7.3 STARTTLS is required to send mail [ZR0P278CA0106.CHEP278.PROD.OUTLOOK.COM]
  </code></pre>
  <p>I got the SMTP server, the encryption method, and the server port from outlook's website from my e-mail settings.</p>
  <p>P.S.: I have <code>smtpuser</code> commented out because I was getting an error that is solved, by <a href="https://stackoverflow.com/a/6444339/8324585">this</a> answer, by removing the <code>smtpuser</code> field.</p>