Authentication

I've been using Gmail to to send confirmation emails when they create new accounts since 2016. It worked like a charm and I also wrote a article for people in need. Last week, my students reported no emails were sent. I don't know why it suddenly stopped due to Moodle or Gmail?

Here's my configuration;

- Site administration / ► Server / ► Email / ► Outgoing mail configuration (moodle 3.x)

- Turn ON less secure ap: https://www.google.com/settings/security/lesssecureapps

P/S: Here's a similar thread: https://moodle.org/mod/forum/discuss.php?d=417878