Plaintext logins with Dovecot and Ubuntu
Disallow plaintext authentication in non-SSL mode?
Webmin permits you to enable non-SSL connections on its Dovecot SSL
Configuration page, but on Ubuntu at least, that edits
by changing 'yes' here to 'no':
disable_plaintext_auth = no
but the same thing also has to be done in /etc/dovecot/dovecot-postfix.conf ... manually for now.