Unable to authenticate Postfix/Dovecot new build

Was following your excellent guides on ‘Build your own email server on Ubuntu’ using 18.04 running on AWS Lightsail server with all relevant ports opened on AWS firewall.
At end of part 2 I’m unable to get Thunderbird to authenticate. I’ve tried all combinations that I can think of!
I’ve also rebuilt the server 3 times following exactly your notes and checking carefully. Some odd things:

  1. There is only an email file for root in /var/mail/ and no email files for any of the other linux users I have created to test the server.
  2. When I check the IP of the server using nmap it shows ports 110, 143, 993, 995 closed.
  3. Telnet to the host on 25 is open (this is normal - yes).
  4. Linux users are not in the mail group

Its obvious I’ve missed something and after three very careful rebuilds following your instructions I haven’t been able to find it.
I welcome your advice.
Best wishes,

  1. This is normal. If other users didn’t receive any email, then there will be no file for them in /var/mail/ directory.
  2. Looks like your Dovecot isn’t running? You can check its status with: systemctl status dovecot
  3. There is no need to add users to the mail group.

Thank you. That was a great help. Yes, Dovecot was not running.
Restarting dovecot revealed the problem - or rather 2 problems. There were additional parentheses in /etc/dovecot/conf.d/10-master.conf at lines 68 and 120. They were in the commented material and only became additional when I copied in the edits.
Everything good now and looking forward to Part 3!

Interesting that the error messages revealed by systemct restart dovecot didn’t appear earlier when dovecot is restarted during Part 2.