imapログイン：接続が失われました。

正常に送受信されるパブリックDNSエントリを持つ電子メールサーバーがあります。

imapアカウントでOutlookに追加しようとしましたが、常に失敗しました。サーバーエラーの表示

Oct 30 15:29:04 mail.example.local dovecot[17250]: imap-login: Disconnected (auth failed, 1 attempts in 4 secs): user=<[email protected]>, method=PLAIN, rip=12.123.456.789, lip=123.4.56.7, session=<yjdfyjfkugih>

Oct 30 15:29:08 mail.example.local auth[17491]: pam_unix(dovecot:auth): check pass; user unknown

cat /etc/pam.d/dovecot
#%PAM-1.0
auth       required     pam_nologin.so
auth       include      password-auth
account    include      password-auth
session    include      password-auth
auth       required     pam_unix.so nullok
account    required     pam_unix.so

cat auth-system.conf.ext PAM authentication. Preferred nowadays by most systems. PAM is typically used with either userdb passwd or userdb static. REMEMBER: You'll need /etc/pam.d/dovecot file created for PAM authentication to actually work. <doc/wiki/PasswordDatabase.PAM.txt> passdb { driver = pam # [session=yes] [setcred=yes] [failure_show_msg=yes] [max_requests=<n>] # [cache_key=<key>] [<service name>] #args = dovecot }