Gmail SMTP login problem

I tried setting my SMTP to gmail, and I had issues signing in.
I tried allow less secure apps to access your account and Display unlock Captcha however both failed me.
In the end I enabled 2-Factor Authentication and used the application password.
Now the mail_room does not die and restart every second.

The mail_room error I was getting was as follows:

/usr/lib/ruby/2.3.0/net/imap.rb:1196:in `get_tagged_response':  Please log in via your web browser: https://support.google.com/mail/accounts/answer/78754 (Failure) (Net::IMAP::NoResponseError)
        from /usr/lib/ruby/2.3.0/net/imap.rb:1250:in `block in send_command'
        from /usr/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
        from /usr/lib/ruby/2.3.0/net/imap.rb:1232:in `send_command'
        from /usr/lib/ruby/2.3.0/net/imap.rb:436:in `login'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/connection.rb:84:in `log_in'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/connection.rb:68:in `setup'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/connection.rb:8:in `initialize'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/mailbox_watcher.rb:57:in `new'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/mailbox_watcher.rb:57:in `connection'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/mailbox_watcher.rb:28:in `run'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/coordinator.rb:19:in `each'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/coordinator.rb:19:in `run'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/lib/mail_room/cli.rb:52:in `start'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/gems/mail_room-0.9.0/bin/mail_room:5:in `<top (required)>'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/bin/mail_room:23:in `load'
        from /home/git/gitlab/vendor/bundle/ruby/2.3.0/bin/mail_room:23:in `<main>'

If anyone else had the same issue, I think it may be helpful to add the necessity of a 2FA to the gmail account in the README.md file.

Start by reading README.md and locating the mail_room or Gmail setup instructions. Done means documenting that Gmail may require 2-Factor Authentication and an application password, based on the reported login failure.