メールサーバー、欲しいですよね？

最近インターネット回線を変えたところOP25Bがなくなったので、じゃあメールサーバー立てようということで書いています。
SSL/TLS認証、SPF、DKIM対応のメールサーバーにしようと思います。

OP25Bとは
https://wa3.i-3-i.info/word14981.html

SPFとかDKIMについて
https://ent.iij.ad.jp/articles/172/

使うツールとか

OS

AlmaLinux 9を使います。

$ cat /etc/redhat-release
AlmaLinux release 9.4 (Seafoam Ocelot)

Postfix

言わずと知れたメール送信サーバーです。

$ postconf | grep mail_version
mail_version = 3.5.9
milter_macro_v = $mail_name $mail_version

Dovecot

言わずとry

 $ dovecot --version
 2.3.16 (7e2e900c1a)

RoundCube

PHPで書かれているオープンソースのWebメーラーです。
Nginxにのっけて動かします。
記事執筆時点で最新のVersion 1.6.7です。

Nginx

PHPとかをのっけます。
今回は別のサーバーでリバースプロキシしてSSL認証かけているので、設定ファイルはhttpのものしか書きません。

$ nginx -version
nginx version: nginx/1.20.1

MariaDB

Roundcubeが使います。

$ mariadb --version
mariadb from 11.4.2-MariaDB, client 15.2 for Linux (x86_64) using  EditLine wrapper

PHP

8.2系を使います。

$ php --version
PHP 8.2.20 (cli) (built: Jun  4 2024 13:22:51) (NTS gcc x86_64)
Copyright (c) The PHP Group
Zend Engine v4.2.20, Copyright (c) Zend Technologies
    with Zend OPcache v8.2.20, Copyright (c), by Zend Technologies

インストール

epel、remi

# dnf install -y epel-release
# dnf install -y https://rpms.remirepo.net/enterprise/remi-release-9.rpm

postfix、Dovecot、nginx、opendkim

# dnf install -y postfix dovecot nginx opendkim

PHP

# dnf remove php-*
# dnf module reset -y php && dnf module enable -y php:remi-8.2
# dnf install -y php php-devel php-mbstring php-mysqlnd php-pdo php-gd php-xml php-intl php-zip php-ldap php-imagick

MariaDB

# curl -sS https://downloads.mariadb.com/MariaDB/mariadb_repo_setup | sudo bash
# yum install mariadb-server MariaDB-client

SPF、MXレコードの設定

次のレコードをお使いのDNSに登録しておいてください。

example.com.      IN MX 10 mail.example.com.
example.com.      IN TXT "v=spf1 自分のIPアドレス ~all"
mail.example.com. IN A 自分のIPアドレス

ポートの開放

送受信用のポートを開放します。

SMTP 25
SMTPS 465
IMAPS 993
POP3S 995

# firewall-cmd --add-port=25/tcp --permanent
# firewall-cmd --add-port=465/tcp --permanent
# firewall-cmd --add-port=993/tcp --permanent
# firewall-cmd --add-port=995/tcp --permanent
# firewall-cmd --reload

SSL証明書

メールのSSL/TLS認証に使う証明書を取得してきてください。
この先では、certbotで取得した前提で進めます。
certbotで証明書を取得した場合のファイルパス /etc/letsencrypt/live/mail.example.com/

各種設定

Postfixの設定

変更点のみ書きます。

メイン設定

/etc/postfix/main.cf

# メールサーバーのホスト名を設定
#myhostname = host.domain.tld
　↓
myhostname = mail.example.com

# メールサーバーのドメイン名を設定
#mydomain = domain.tld
　↓
mydomain = example.com

# メールアドレスを「ユーザ名@ドメイン名」の形式で使えるようにする
#myorigin = $mydomain
　↓
myorigin = $mydomain

# 全てのホストからメールを受信する
inet_interfaces = localhost
　↓
inet_interfaces = all

# mydomain = で指定したドメイン宛のメールを受信する
mydestination = $myhostname, localhost.$mydomain, localhost
　↓
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain

# 存在しないメールアドレス(ユーザ)宛のメールの受信を拒否する
#local_recipient_maps = proxy:unix:passwd.byname $alias_maps
　↓
local_recipient_maps = proxy:unix:passwd.byname $alias_maps

# メールの格納フォーマットの指定
#home_mailbox = Maildir/
　↓
home_mailbox = Maildir/

# 不要な情報を公開しない
#smtpd_banner = $myhostname ESMTP $mail_name
　↓
smtpd_banner = $myhostname ESMTP

# サーバ証明書を指定
smtpd_tls_cert_file = /etc/pki/tls/certs/postfix.pem
　↓
smtpd_tls_cert_file = /etc/letsencrypt/live/mail.example.com/fullchain.pem

# サーバ秘密鍵を指定
smtpd_tls_key_file = /etc/pki/tls/private/postfix.key
　↓
smtpd_tls_key_file = /etc/letsencrypt/live/mail.example.com/privkey.pem

# 以下を末尾に追加
disable_vrfy_command = yes
mailbox_size_limit = 0
message_size_limit = 256000000
########## SMTP-Auth関連 ##########
# SASL認証を有効化
smtpd_sasl_auth_enable = yes

# Dovecot SASL ライブラリを指定
smtpd_sasl_type = dovecot

# Dovecot SASL ライブラリの認証ソケットファイル　/var/spool/postfix/ からの相対パスで記述
smtpd_sasl_path = private/auth

# 古いバージョンの AUTH コマンド (RFC 2554) を実装した SMTP クライアントとの相互運用性を有効にする
broken_sasl_auth_clients = yes

# 認証を通過したものはリレーを許可する（permit_sasl_authenticated）
smtpd_recipient_restrictions =
    permit_mynetworks
    permit_sasl_authenticated
    reject_unauth_destination

########## TLS/SSL関連 ##########
# TLSログレベルの設定
# 0:出力しない　1:TLSハンドシェイクと証明書情報　2:TLSネゴシエーションの全て
smtpd_tls_loglevel = 1

# 暗号に関する情報を "Received:" メッセージヘッダに含める
smtpd_tls_received_header = yes

# 接続キャッシュファイルの指定
smtpd_tls_session_cache_database = btree:/var/lib/postfix/smtpd_scache

# キャッシュの保持時間の指定
smtpd_tls_session_cache_timeout = 3600s

#DKIM利用
smtpd_milters = inet:127.0.0.1:8891
non_smtpd_milters = inet:localhost:8891
milter_default_action = accept

SMTPS設定

/etc/postfix/master.cf

#smtps     inet  n       -       n       -       -       smtpd
#  -o syslog_name=postfix/smtps
#  -o smtpd_tls_wrappermode=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_client_restrictions=$mua_client_restrictions
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
#  -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING

　↓

# コメントインします
smtps     inet  n       -       n       -       -       smtpd
#  -o syslog_name=postfix/smtps
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_client_restrictions=$mua_client_restrictions
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
  -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING

ルックアップテーブルを作成

# postmap /etc/postfix/access

Postfixの起動&自動起動設定

# systemctl enable --now postfix

Dovecotの設定

受信プロトコルの設定

dovecot.conf

#protocols = imap pop3 lmtp submission
　↓

# POP3とIMAPのみに限定
protocols = imap pop3

IMAPS、POP3Sを有効化し、IMAPとPOP3を無効化

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

service imap-login {
  inet_listener imap {
    #port = 143
	　↓
    port = 0
  }
  inet_listener imaps {
    #port = 993
    #ssl = yes
	　↓
    port = 993
    ssl = yes
  }
}

service pop3-login {
  inet_listener pop3 {
    #port = 110
	　↓
    port = 0
  }
  inet_listener pop3s {
    #port = 995
    #ssl = yes
	　↓
    port = 995
    ssl = yes
  }
}

SASLライブラリのソケットを設定

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

service auth {
  # auth_socket_path points to this userdb socket by default. It's typically
  # used by dovecot-lda, doveadm, possibly imap process, etc. Users that have
  # full permissions to this socket are able to get a list of all usernames and
  # get the results of everyone's userdb lookups.
  #
  # The default 0666 mode allows anyone to connect to the socket, but the
  # userdb lookups will succeed only if the userdb returns an "uid" field that
  # matches the caller process's UID. Also if caller's uid or gid matches the
  # socket's uid or gid the lookup succeeds. Anything else causes a failure.
  #
  # To give the caller full permissions to lookup all users, set the mode to
  # something else than 0666 and Dovecot lets the kernel enforce the
  # permissions (e.g. 0777 allows everyone full permissions).
  unix_listener auth-userdb {
    #mode = 0666
    #user = 
    #group = 
  }

  # Postfix smtp-auth
  #unix_listener /var/spool/postfix/private/auth {
  #  mode = 0666
  #}

  ↓

  # Postfix smtp-auth
  unix_listener /var/spool/postfix/private/auth {
    mode = 0666
    user = postfix
    group = postfix
  }

認証方式の設定

平文認証を許可していますが、SSL/TLSを使うので問題ありません。

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

#disable_plaintext_auth = yes
　↓
disable_plaintext_auth = no

auth_mechanisms = plain
　↓
auth_mechanisms = plain login

SSL/TLSの有効化

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

ssl = required
　↓
ssl = yes


ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
ssl_key = </etc/pki/dovecot/private/dovecot.pem
　↓
ssl_cert = </etc/letsencrypt/live/mail.example.com/fullchain.pem
ssl_key = </etc/letsencrypt/live/mail.example.com/privkey.pem

メールボックスの場所を指定

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

#mail_location = 
　↓
mail_location = maildir:~/Maildir

Thunderbirdでのアカウント設定例

ユーザー名はLinuxユーザー名をそのまま使います。

オープンリレーチェック

迷惑メールなどの踏み台にされないよう、オープンリレーチェックを行います。

サーバーアドレスを入力して数分待つと、次のように結果が出力されるのですべてRelay NOT Acceptedになっているか確認してください。

DKIMの設定

OpenDKIMをすでにインストールしているので、設定から始めます。

秘密鍵と公開鍵の作成

opendkim-genkeyコマンドでキーペアを生成します。

キーペアの生成場所作成

# mkdir /etc/opendkim/keys/example.com

キーペア生成

引数の説明は次の通りです。

-b 鍵長
-D 出力先ディレクトリ
-d ドメイン
-s セレクタ
セレクタは署名時にどのキーペアを使うか指定するものなので、覚えやすいものにすると良いと思います。

# opendkim-genkey -b 1024 -D /etc/opendkim/keys/example.com -d example.com -s default

所有者変更

# chown -R opendkim:opendkim /etc/opendkim/keys/

コンフィグ編集

それぞれ書き換えてください。

/etc/opendkim.conf

Mode v
  ↓
Mode sv

Socket  inet:8891@localhost

KeyTable        /etc/opendkim/KeyTable

SigningTable    refile:/etc/opendkim/SigningTable

ExternalIgnoreList   /etc/opendkim/TrustedHosts

InternalHosts   /etc/opendkim/TrustedHosts

SigningTableのレコード設定

メールアドレスと秘密鍵を関連付けます。
基本的なフォーマットは次のようになっています。

*@ドメイン名 セレクタ._domainkey.ドメイン名

/etc/opendkim/SigningTable

*@example.com default._domainkey.example.com

KeyTableのレコード設定

DKIMレコードと秘密鍵を関連付けます。
基本的なフォーマットは次のようになっています。

セレクタ._domainkey.ドメイン名 ドメイン名:セレクタ名:秘密鍵パス

/etc/opendkim/KeyTable

default._domainkey.example.com example.com:default:/etc/opendkim/keys/example.com/default.private

設定が終わったらサービスを再起動します。

# systemctl restart postfix dovecot opendkim

RoundCubeの設定

RoundCubeのダウンロード、配置

最新版のCompleteをダウンロードして、展開されたディレクトリをmailに改名します。

# tar zxvf roundcubemail-1.6.7-complete.tar.gz
# mv roundcubemail-1.6.7/ mail/
# mv mail/ /var/www/html/

PHPのコンフィグ編集

次のファイルを使えば動くと思います。

PHPコンフィグファイル

/etc/php-fpm.d/www.conf

; Start a new pool named 'www'.
; the variable $pool can be used in any directive and will be replaced by the
; pool name ('www' here)
[www]

; Per pool prefix
; It only applies on the following directives:
; - 'access.log'
; - 'slowlog'
; - 'listen' (unixsocket)
; - 'chroot'
; - 'chdir'
; - 'php_values'
; - 'php_admin_values'
; When not set, the global prefix (or @php_fpm_prefix@) applies instead.
; Note: This directive can also be relative to the global prefix.
; Default Value: none
;prefix = /path/to/pools/$pool

; Unix user/group of processes
; Note: The user is mandatory. If the group is not set, the default user's group
;       will be used.
; RPM: apache user chosen to provide access to the same directories as httpd
user = nginx
; RPM: Keep a group allowed to write in log dir.
group = nginx

; The address on which to accept FastCGI requests.
; Valid syntaxes are:
;   'ip.add.re.ss:port'    - to listen on a TCP socket to a specific IPv4 address on
;                            a specific port;
;   '[ip:6:addr:ess]:port' - to listen on a TCP socket to a specific IPv6 address on
;                            a specific port;
;   'port'                 - to listen on a TCP socket to all addresses
;                            (IPv6 and IPv4-mapped) on a specific port;
;   '/path/to/unix/socket' - to listen on a unix socket.
; Note: This value is mandatory.
listen = /run/php-fpm/www.sock

; Set listen(2) backlog.
; Default Value: 511
;listen.backlog = 511

; Set permissions for unix socket, if one is used. In Linux, read/write
; permissions must be set in order to allow connections from a web server.
; Default Values: user and group are set as the running user
;                 mode is set to 0660
listen.owner = nginx
listen.group = nginx
listen.mode = 0660

; When POSIX Access Control Lists are supported you can set them using
; these options, value is a comma separated list of user/group names.
; When set, listen.owner and listen.group are ignored
listen.acl_users = apache,nginx
;listen.acl_groups =

; List of addresses (IPv4/IPv6) of FastCGI clients which are allowed to connect.
; Equivalent to the FCGI_WEB_SERVER_ADDRS environment variable in the original
; PHP FCGI (5.2.2+). Makes sense only with a tcp listening socket. Each address
; must be separated by a comma. If this value is left blank, connections will be
; accepted from any ip address.
; Default Value: any
listen.allowed_clients = 127.0.0.1

; Specify the nice(2) priority to apply to the pool processes (only if set)
; The value can vary from -19 (highest priority) to 20 (lower priority)
; Note: - It will only work if the FPM master process is launched as root
;       - The pool processes will inherit the master process priority
;         unless it specified otherwise
; Default Value: no set
; process.priority = -19

; Set the process dumpable flag (PR_SET_DUMPABLE prctl) even if the process user
; or group is differrent than the master process user. It allows to create process
; core dump and ptrace the process for the pool user.
; Default Value: no
; process.dumpable = yes

; Choose how the process manager will control the number of child processes.
; Possible Values:
;   static  - a fixed number (pm.max_children) of child processes;
;   dynamic - the number of child processes are set dynamically based on the
;             following directives. With this process management, there will be
;             always at least 1 children.
;             pm.max_children      - the maximum number of children that can
;                                    be alive at the same time.
;             pm.start_servers     - the number of children created on startup.
;             pm.min_spare_servers - the minimum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is less than this
;                                    number then some children will be created.
;             pm.max_spare_servers - the maximum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is greater than this
;                                    number then some children will be killed.
;  ondemand - no children are created at startup. Children will be forked when
;             new requests will connect. The following parameter are used:
;             pm.max_children           - the maximum number of children that
;                                         can be alive at the same time.
;             pm.process_idle_timeout   - The number of seconds after which
;                                         an idle process will be killed.
; Note: This value is mandatory.
pm = dynamic

; The number of child processes to be created when pm is set to 'static' and the
; maximum number of child processes when pm is set to 'dynamic' or 'ondemand'.
; This value sets the limit on the number of simultaneous requests that will be
; served. Equivalent to the ApacheMaxClients directive with mpm_prefork.
; Equivalent to the PHP_FCGI_CHILDREN environment variable in the original PHP
; CGI. The below defaults are based on a server without much resources. Don't
; forget to tweak pm.* to fit your needs.
; Note: Used when pm is set to 'static', 'dynamic' or 'ondemand'
; Note: This value is mandatory.
pm.max_children = 50

; The number of child processes created on startup.
; Note: Used only when pm is set to 'dynamic'
; Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2
pm.start_servers = 5

; The desired minimum number of idle server processes.
; Note: Used only when pm is set to 'dynamic'
; Note: Mandatory when pm is set to 'dynamic'
pm.min_spare_servers = 5

; The desired maximum number of idle server processes.
; Note: Used only when pm is set to 'dynamic'
; Note: Mandatory when pm is set to 'dynamic'
pm.max_spare_servers = 35

; The number of seconds after which an idle process will be killed.
; Note: Used only when pm is set to 'ondemand'
; Default Value: 10s
;pm.process_idle_timeout = 10s;

; The number of requests each child process should execute before respawning.
; This can be useful to work around memory leaks in 3rd party libraries. For
; endless request processing specify '0'. Equivalent to PHP_FCGI_MAX_REQUESTS.
; Default Value: 0
;pm.max_requests = 500

; The URI to view the FPM status page. If this value is not set, no URI will be
; recognized as a status page. It shows the following informations:
;   pool                 - the name of the pool;
;   process manager      - static, dynamic or ondemand;
;   start time           - the date and time FPM has started;
;   start since          - number of seconds since FPM has started;
;   accepted conn        - the number of request accepted by the pool;
;   listen queue         - the number of request in the queue of pending
;                          connections (see backlog in listen(2));
;   max listen queue     - the maximum number of requests in the queue
;                          of pending connections since FPM has started;
;   listen queue len     - the size of the socket queue of pending connections;
;   idle processes       - the number of idle processes;
;   active processes     - the number of active processes;
;   total processes      - the number of idle + active processes;
;   max active processes - the maximum number of active processes since FPM
;                          has started;
;   max children reached - number of times, the process limit has been reached,
;                          when pm tries to start more children (works only for
;                          pm 'dynamic' and 'ondemand');
; Value are updated in real time.
; Example output:
;   pool:                 www
;   process manager:      static
;   start time:           01/Jul/2011:17:53:49 +0200
;   start since:          62636
;   accepted conn:        190460
;   listen queue:         0
;   max listen queue:     1
;   listen queue len:     42
;   idle processes:       4
;   active processes:     11
;   total processes:      15
;   max active processes: 12
;   max children reached: 0
;
; By default the status page output is formatted as text/plain. Passing either
; 'html', 'xml' or 'json' in the query string will return the corresponding
; output syntax. Example:
;   http://www.foo.bar/status
;   http://www.foo.bar/status?json
;   http://www.foo.bar/status?html
;   http://www.foo.bar/status?xml
;
; By default the status page only outputs short status. Passing 'full' in the
; query string will also return status for each pool process.
; Example:
;   http://www.foo.bar/status?full
;   http://www.foo.bar/status?json&full
;   http://www.foo.bar/status?html&full
;   http://www.foo.bar/status?xml&full
; The Full status returns for each process:
;   pid                  - the PID of the process;
;   state                - the state of the process (Idle, Running, ...);
;   start time           - the date and time the process has started;
;   start since          - the number of seconds since the process has started;
;   requests             - the number of requests the process has served;
;   request duration     - the duration in µs of the requests;
;   request method       - the request method (GET, POST, ...);
;   request URI          - the request URI with the query string;
;   content length       - the content length of the request (only with POST);
;   user                 - the user (PHP_AUTH_USER) (or '-' if not set);
;   script               - the main script called (or '-' if not set);
;   last request cpu     - the %cpu the last request consumed
;                          it's always 0 if the process is not in Idle state
;                          because CPU calculation is done when the request
;                          processing has terminated;
;   last request memory  - the max amount of memory the last request consumed
;                          it's always 0 if the process is not in Idle state
;                          because memory calculation is done when the request
;                          processing has terminated;
; If the process is in Idle state, then informations are related to the
; last request the process has served. Otherwise informations are related to
; the current request being served.
; Example output:
;   ************************
;   pid:                  31330
;   state:                Running
;   start time:           01/Jul/2011:17:53:49 +0200
;   start since:          63087
;   requests:             12808
;   request duration:     1250261
;   request method:       GET
;   request URI:          /test_mem.php?N=10000
;   content length:       0
;   user:                 -
;   script:               /home/fat/web/docs/php/test_mem.php
;   last request cpu:     0.00
;   last request memory:  0
;
; Note: There is a real-time FPM status monitoring sample web page available
;       It's available in: @EXPANDED_DATADIR@/fpm/status.html
;
; Note: The value must start with a leading slash (/). The value can be
;       anything, but it may not be a good idea to use the .php extension or it
;       may conflict with a real PHP file.
; Default Value: not set
;pm.status_path = /status

; The ping URI to call the monitoring page of FPM. If this value is not set, no
; URI will be recognized as a ping page. This could be used to test from outside
; that FPM is alive and responding, or to
; - create a graph of FPM availability (rrd or such);
; - remove a server from a group if it is not responding (load balancing);
; - trigger alerts for the operating team (24/7).
; Note: The value must start with a leading slash (/). The value can be
;       anything, but it may not be a good idea to use the .php extension or it
;       may conflict with a real PHP file.
; Default Value: not set
;ping.path = /ping

; This directive may be used to customize the response of a ping request. The
; response is formatted as text/plain with a 200 response code.
; Default Value: pong
;ping.response = pong

; The access log file
; Default: not set
;access.log = log/$pool.access.log

; The access log format.
; The following syntax is allowed
;  %%: the '%' character
;  %C: %CPU used by the request
;      it can accept the following format:
;      - %{user}C for user CPU only
;      - %{system}C for system CPU only
;      - %{total}C  for user + system CPU (default)
;  %d: time taken to serve the request
;      it can accept the following format:
;      - %{seconds}d (default)
;      - %{miliseconds}d
;      - %{mili}d
;      - %{microseconds}d
;      - %{micro}d
;  %e: an environment variable (same as $_ENV or $_SERVER)
;      it must be associated with embraces to specify the name of the env
;      variable. Some exemples:
;      - server specifics like: %{REQUEST_METHOD}e or %{SERVER_PROTOCOL}e
;      - HTTP headers like: %{HTTP_HOST}e or %{HTTP_USER_AGENT}e
;  %f: script filename
;  %l: content-length of the request (for POST request only)
;  %m: request method
;  %M: peak of memory allocated by PHP
;      it can accept the following format:
;      - %{bytes}M (default)
;      - %{kilobytes}M
;      - %{kilo}M
;      - %{megabytes}M
;      - %{mega}M
;  %n: pool name
;  %o: output header
;      it must be associated with embraces to specify the name of the header:
;      - %{Content-Type}o
;      - %{X-Powered-By}o
;      - %{Transfert-Encoding}o
;      - ....
;  %p: PID of the child that serviced the request
;  %P: PID of the parent of the child that serviced the request
;  %q: the query string
;  %Q: the '?' character if query string exists
;  %r: the request URI (without the query string, see %q and %Q)
;  %R: remote IP address
;  %s: status (response code)
;  %t: server time the request was received
;      it can accept a strftime(3) format:
;      %d/%b/%Y:%H:%M:%S %z (default)
;      The strftime(3) format must be encapsuled in a %{<strftime_format>}t tag
;      e.g. for a ISO8601 formatted timestring, use: %{%Y-%m-%dT%H:%M:%S%z}t
;  %T: time the log has been written (the request has finished)
;      it can accept a strftime(3) format:
;      %d/%b/%Y:%H:%M:%S %z (default)
;      The strftime(3) format must be encapsuled in a %{<strftime_format>}t tag
;      e.g. for a ISO8601 formatted timestring, use: %{%Y-%m-%dT%H:%M:%S%z}t
;  %u: remote user
;
; Default: "%R - %u %t \"%m %r\" %s"
;access.format = "%R - %u %t \"%m %r%Q%q\" %s %f %{mili}d %{kilo}M %C%%"

; The log file for slow requests
; Default Value: not set
; Note: slowlog is mandatory if request_slowlog_timeout is set
slowlog = /var/log/php-fpm/www-slow.log

; The timeout for serving a single request after which a PHP backtrace will be
; dumped to the 'slowlog' file. A value of '0s' means 'off'.
; Available units: s(econds)(default), m(inutes), h(ours), or d(ays)
; Default Value: 0
;request_slowlog_timeout = 0

; Depth of slow log stack trace.
; Default Value: 20
;request_slowlog_trace_depth = 20

; The timeout for serving a single request after which the worker process will
; be killed. This option should be used when the 'max_execution_time' ini option
; does not stop script execution for some reason. A value of '0' means 'off'.
; Available units: s(econds)(default), m(inutes), h(ours), or d(ays)
; Default Value: 0
;request_terminate_timeout = 0

; Set open file descriptor rlimit.
; Default Value: system defined value
;rlimit_files = 1024

; Set max core size rlimit.
; Possible Values: 'unlimited' or an integer greater or equal to 0
; Default Value: system defined value
;rlimit_core = 0

; Chroot to this directory at the start. This value must be defined as an
; absolute path. When this value is not set, chroot is not used.
; Note: you can prefix with '$prefix' to chroot to the pool prefix or one
; of its subdirectories. If the pool prefix is not set, the global prefix
; will be used instead.
; Note: chrooting is a great security feature and should be used whenever
;       possible. However, all PHP paths will be relative to the chroot
;       (error_log, sessions.save_path, ...).
; Default Value: not set
;chroot =

; Chdir to this directory at the start.
; Note: relative path can be used.
; Default Value: current directory or / when chroot
;chdir = /var/www

; Redirect worker stdout and stderr into main error log. If not set, stdout and
; stderr will be redirected to /dev/null according to FastCGI specs.
; Note: on highloaded environement, this can cause some delay in the page
; process time (several ms).
; Default Value: no
;catch_workers_output = yes

; Clear environment in FPM workers
; Prevents arbitrary environment variables from reaching FPM worker processes
; by clearing the environment in workers before env vars specified in this
; pool configuration are added.
; Setting to "no" will make all environment variables available to PHP code
; via getenv(), $_ENV and $_SERVER.
; Default Value: yes
;clear_env = no

; Limits the extensions of the main script FPM will allow to parse. This can
; prevent configuration mistakes on the web server side. You should only limit
; FPM to .php extensions to prevent malicious users to use other extensions to
; execute php code.
; Note: set an empty value to allow all extensions.
; Default Value: .php
;security.limit_extensions = .php .php3 .php4 .php5 .php7

; Pass environment variables like LD_LIBRARY_PATH. All $VARIABLEs are taken from
; the current environment.
; Default Value: clean env
;env[HOSTNAME] = $HOSTNAME
;env[PATH] = /usr/local/bin:/usr/bin:/bin
;env[TMP] = /tmp
;env[TMPDIR] = /tmp
;env[TEMP] = /tmp

; Additional php.ini defines, specific to this pool of workers. These settings
; overwrite the values previously defined in the php.ini. The directives are the
; same as the PHP SAPI:
;   php_value/php_flag             - you can set classic ini defines which can
;                                    be overwritten from PHP call 'ini_set'.
;   php_admin_value/php_admin_flag - these directives won't be overwritten by
;                                     PHP call 'ini_set'
; For php_*flag, valid values are on, off, 1, 0, true, false, yes or no.

; Defining 'extension' will load the corresponding shared extension from
; extension_dir. Defining 'disable_functions' or 'disable_classes' will not
; overwrite previously defined php.ini values, but will append the new value
; instead.

; Note: path INI options can be relative and will be expanded with the prefix
; (pool, global or @prefix@)

; Default Value: nothing is defined by default except the values in php.ini and
;                specified at startup with the -d argument
;php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i -f www@my.domain.com
;php_flag[display_errors] = off
php_admin_value[error_log] = /var/log/php-fpm/www-error.log
php_admin_flag[log_errors] = on
;php_admin_value[memory_limit] = 128M

; Set the following data paths to directories owned by the FPM process user.
;
; Do not change the ownership of existing system directories, if the process
; user does not have write permission, create dedicated directories for this
; purpose.
;
; See warning about choosing the location of these directories on your system
; at http://php.net/session.save-path
php_value[session.save_handler] = files
php_value[session.save_path]    = /var/lib/php/session
php_value[soap.wsdl_cache_dir]  = /var/lib/php/wsdlcache
;php_value[opcache.file_cache]  = /var/lib/php/opcache

php_admin_value[open_basedir] = /tmp/:/var/cache/roundcubemail:/var/lib/roundcubemail:/usr/share/webapps/roundcubemail:/etc/webapps/roundcubemail:/usr/share/pear/:/var/log/roundcubemail:/var/www/html/mail

Nginxの設定

コンフィグファイル

SSLなどはお好みで追加してください。
HTTPのみ書きます。

/etc/nginx/conf.d/mail.conf

server {
    listen 80;
    server_name _;

    root /var/www/html/mail;
    index index.php index.html index.htm;

    # ログの設定
    access_log /var/log/nginx/roundcube.access.log;
    error_log /var/log/nginx/roundcube.error.log;

    # Roundcubeのドキュメントルート
    location / {
        try_files $uri $uri/ /index.php;
    }

    # 静的ファイルの処理
    location ~* \.(jpg|jpeg|gif|css|png|js|ico|html|xml|txt|pdf|eot|ttf|woff|woff2)$ {
        access_log off;
        log_not_found off;
        expires max;
    }

    # PHPファイルの処理
    location ~ \.php$ {
        try_files $uri =404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass unix:/run/php-fpm/www.sock;
        fastcgi_index index.php;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param PATH_INFO $fastcgi_path_info;
    }

    # .htaccessの拒否
    location ~ /\.ht {
        deny all;
    }

    # セキュリティのためのディレクトリの制限
    location ~ ^/(config|temp|logs)/ {
        deny all;
    }
}

MariaDBの設定

mariadb_secure_installation

mariadb-secure-installationで、初期設定をします。

#  mariadb-secure-installation
Enter current password for root (enter for none): Enter押下

Change the root password? [Y/n] Y
rootパスワードを設定してください。

Switch to unix_socket authentication [Y/n] n

Remove anonymous users? [Y/n] Y

Disallow root login remotely? [Y/n] Y

Remove test database and access to it? [Y/n] Y

Reload privilege tables now? [Y/n] Y

データベース作成

# mariadb -u root -p
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 54
Server version: 11.4.2-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]>

> CREATE USER 'roundcube' IDENTIFIED BY '自分でパスワードを決める'; # roundcubeユーザー作成
> CREATE DATABASE roundcube;                                      # roundcubeデータベース作成
> GRANT ALL PRIVILEGES ON roundcube.* TO 'roundcube';             # roundcubeユーザーのroundcubeデータベースへのアクセス許可
> FLUSH PRIVILEGES;
> EXIT;

roundcubeのテンプレートを流し込みます。

# mariadb -u roundcube -p roundcube < /var/www/html/mail/SQL/mysql.initial.sql

ブラウザでのインストール実行

http://サーバーのIPにアクセスし、NOT OKが無いことを確認してください。

Nextを押して次に進みます。

この先はほとんどデフォルトの設定で構いません。

Product Nameはデフォルトでも構いませんが、変更するとブラウザのタイトルなどが変わります。

Database Setupに先ほど設定した内容を入れます。
Database Server -> localhost
Database Name -> roundcube
Database username -> roundcube
Database Password -> 先ほど設定したパスワード

IMAP、SMTP設定

SMTP_HOSTがtls://になっていますがこれは私の設定ミスなので、ssl://mail.example.comの形式にしてください。

言語設定

Languageをja_JPにします。

送信テスト

ここまで終わったらブラウザでhttp://サーバーアドレスにアクセスすると、roundcubeのログイン画面が見られるはずです。

Linuxユーザーのユーザー名とパスワードでログインして、メール新規作成で送信してみましょう。

送信テスト

送信メールのセキュリティヘッダー

SPF、DKIMが両方ともPASSになっていて、SPFのIPアドレスとDKIMシグネチャーがDNSに登録したものと一致していますので、正常な動作が確認できました。

受信テスト

Gmailから送信してみます。

こちらも正常に動作しました。

おわり

お疲れさまでした。
DMARCやADSPの設定はここでは取り上げていませんが、設定しておくことをお勧めします。