Dovecotのインストール

# apt install dovecot-core dovecot-lmtpd dovecot-mysql dovecot-pop3d dovecot-imapd

# nano /etc/dovecot/conf.d/10-mail.conf

# 30行目
mail_location = maildir:/var/vmail/%d/%n

# 108行目・109行目
mail_uid = vmail 
mail_gid = mail 

# 178行目・179行目
first_valid_uid = 150
last_valid_uid = 150

# nano /etc/dovecot/conf.d/10-auth.conf

# 10行目：コメント解除して変更 (プレーンテキスト認証も許可)
disable_plaintext_auth = no

# 100行目：追記
auth_mechanisms = plain login

# 122行目：コメント化
#!include auth-system.conf.ext

# 123行目：コメント解除
!include auth-sql.conf.ext

# nano /etc/dovecot/dovecot-sql.conf.ext

# 32行目：
driver = mysql

# 75行目：追加する
connect = host=localhost dbname=postfixadmin user=postfixadmin password=strongPassword

# 82行目：MD5 を MD5-CRY へ変更する
default_pass_scheme = MD5-CRYPT

# 114行目：追加する
password_query = SELECT username as user, password, '/var/vmail/%d/%n' as userdb_home, 'maildir:/var/vmail/%d/%n' as userdb_mail, 150 as userdb_uid, 8 as userdb_gid FROM mailbox WHERE username = '%u' AND active = '1'

# 135行目：追加する
user_query = SELECT '/var/vmail/%d/%u' as home, 'maildir:/var/vmail/%d/%u' as mail, 150 AS uid, 8 AS gid, concat('dirsize:storage=', quota) AS quota FROM mailbox WHERE username = '%u' AND active = '1'

# nano /etc/dovecot/conf.d/10-ssl.conf

# 6行目：変更
ssl = yes

# nano /etc/dovecot/conf.d/15-lda.conf

# 7行目：追加
postmaster_address = postmaster@yourdomain.com

# nano /etc/dovecot/conf.d/10-master.conf

# 19行目：コメント解除
port = 143
# 23・24行目：コメント解除
port = 993
ssl = yes

# 40行目：コメント解除
port = 110
# 43・44行目：コメント解除
port = 995
ssl = yes

# 55行目から3行コメント化
#unix_listener lmtp {
   #mode = 0666
#}
# 以下を追加
unix_listener /var/spool/postfix/private/dovecot-lmtp {
  mode = 0600
  user = postfix
  group = postfix
}

# 105行目からを以下に修正
unix_listener auth-userdb { 
  mode = 0600 
  user = vmail 
}
# 112行目からを以下に修正
unix_listener /var/pool/postfix/private/auth { 
  mode = 0666 
  user = postfix 
  group = postfix 
} 
# 120行目に追加
user = dovecot 

# 123行目からを以下に修正
service auth-worker { 
  user = vmail 
}

# chown -R vmail:dovecot /etc/dovecot 
# chmod -R o-rwx /etc/dovecot

# systemctl restart dovecot