One of my server stop logging such messages when user trying to login. imap-login: Login: user=username@example.com. I check configuration from another server and it very same.
I'm running on debian testing with config below. # 1.0.5: /etc/dovecot/dovecot.conf log_path: /var/log/dovecot.log info_log_path: /var/log/dovecot.info protocols: imap ssl_cert_file: /etc/postfix/new_chained.crt ssl_key_file: /etc/postfix/mail.pem login_dir: /var/run/dovecot/login login_executable: /usr/lib/dovecot/imap-login login_greeting_capability: yes mail_location: maildir:/var/mail/store/%u dotlock_use_excl: yes maildir_copy_with_hardlinks: yes auth default: mechanisms: PLAIN CRAM-MD5 passdb: driver: passwd-file args: /etc/dovecot/passwd userdb: driver: static args: uid=vmail gid=vmail home=/var/mail/store/%u socket: type: listen client: path: /var/spool/postfix/private/auth mode: 432 user: postfix group: postfix master: path: /var/run/dovecot/auth-master mode: 438 user: root group: root plugin: sieve: /var/mail/store/%u/sieve