サーバーからメールを発信させるための、SMTP(Simple Mail Transfer Protocol)の基本的なインストールおよび設定方法です。
SMTPにはフリーウェアのPostfixを使います。
環境
- Ubuntu24.04 LTS
Postfixのインストール
# apt -y install postfix
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
libnsl2
Suggested packages:
mail-reader postfix-cdb postfix-doc postfix-ldap postfix-lmdb
postfix-mta-sts-resolver postfix-mysql postfix-pcre postfix-pgsql
postfix-sqlite procmail sasl2-bin | dovecot-common
The following NEW packages will be installed:
libnsl2 postfix
0 upgraded, 2 newly installed, 0 to remove and 35 not upgraded.
Need to get 1296 kB of archives.
After this operation, 4321 kB of additional disk space will be used.
Get:1 http://nova.clouds.archive.ubuntu.com/ubuntu noble/main amd64 libnsl2 amd64 1.3.0-3build3 [41.4 kB]
Get:2 http://nova.clouds.archive.ubuntu.com/ubuntu noble/main amd64 postfix amd64 3.8.6-1build2 [1254 kB]
Fetched 1296 kB in 3s (482 kB/s)
Preconfiguring packages ...インストール中に下図の画面になります。
→キーでOKをアクティブにし、エンターを押します。
画面が下図に変わります。
カーソルキーでNo configurationを選択しエンターを押します。
CUI状態にもどり、インストールが進みます。
Selecting previously unselected package libnsl2:amd64.
(Reading database ... 106518 files and directories currently installed.)
Preparing to unpack .../libnsl2_1.3.0-3build3_amd64.deb ...
Unpacking libnsl2:amd64 (1.3.0-3build3) ...
Selecting previously unselected package postfix.
Preparing to unpack .../postfix_3.8.6-1build2_amd64.deb ...
Unpacking postfix (3.8.6-1build2) ...
Setting up libnsl2:amd64 (1.3.0-3build3) ...
Setting up postfix (3.8.6-1build2) ...
info: Selecting GID from range 100 to 999 ...
info: Adding group `postfix' (GID 115) ...
info: Selecting UID from range 100 to 999 ...
info: Adding system user `postfix' (UID 112) ...
info: Adding new user `postfix' (UID 112) with group `postfix' ...
info: Not creating home directory `/var/spool/postfix'.
Creating /etc/postfix/dynamicmaps.cf
info: Selecting GID from range 100 to 999 ...
info: Adding group `postdrop' (GID 116) ...
/etc/aliases does not exist, creating it.
Postfix (main.cf) was not set up. Start with
cp /usr/share/postfix/main.cf.debian /etc/postfix/main.cf
. If you need to make changes, edit /etc/postfix/main.cf (and others) as
needed. To view Postfix configuration values, see postconf(1).
After modifying main.cf, be sure to run 'systemctl reload postfix'.
Created symlink /etc/systemd/system/multi-user.target.wants/postfix.service → /usr/lib/systemd/system/postfix.service.
Processing triggers for rsyslog (8.2312.0-3ubuntu9) ...
Processing triggers for ufw (0.36.2-6) ...
Rules updated for profile 'Apache Full'
Skipped reloading firewall
Processing triggers for man-db (2.12.0-4build2) ...
Processing triggers for libc-bin (2.39-0ubuntu8.2) ...
Scanning processes...
Scanning candidates...
Scanning linux images...
Pending kernel upgrade!
Running kernel version:
6.8.0-31-generic
Diagnostics:
The currently running kernel version is not the expected kernel version
6.8.0-36-generic.
Restarting the system to load the new kernel will not be handled automatically,
so you should consider rebooting.
Restarting services...
Service restarts being deferred:
/etc/needrestart/restart.d/dbus.service
systemctl restart getty@tty1.service
systemctl restart serial-getty@ttyS0.service
systemctl restart systemd-logind.service
systemctl restart unattended-upgrades.service
No containers need to be restarted.
No user sessions are running outdated binaries.
No VM guests are running outdated hypervisor (qemu) binaries on this host.Postfixのバージョン確認
postconfだと情報が多すぎるので、grepで必要部分のみにします。
# postconf | grep mail_version
mail_version = 3.8.6
milter_macro_v = $mail_name $mail_versionPostfixの設定
ベースとなる設定ファイルをコピー
# cp /usr/share/postfix/main.cf.dist /etc/postfix/main.cf設定ファイルの編集
viでmain.cfを編集します。
# vi /etc/postfix/main.cf変更する内容は以下の通りです。
# 基本設定
myhostname = mail.example.com
mydomain = example.com
myorigin = $mydomain
# ネットワーク設定
inet_interfaces = all
inet_protocols = ipv4
# メールボックス設定
home_mailbox = Maildir/
# デフォルトのメールキューおよびメールコマンドパス
mailq_path = /usr/bin/mailq.postfix
newaliases_path = /usr/bin/newaliases.postfix
setgid_group = postdrop
sendmail_path = /usr/sbin/sendmail.postfix
# ドキュメントディレクトリの設定
manpage_directory = /usr/share/man
sample_directory = /usr/share/doc/postfix/samples
readme_directory = /usr/share/doc/postfix/README_FILES
html_directory = /usr/share/doc/postfix/html長くなりますが、参考に中身を出力しています。
# Global Postfix configuration file. This file lists only a subset
# of all parameters. For the syntax, and for a complete parameter
# list, see the postconf(5) manual page (command: "man 5 postconf").
#
# TIP: use the command "postconf -n" to view main.cf parameter
# settings, "postconf parametername" to view a specific parameter,
# and "postconf 'parametername=value'" to set a specific parameter.
#
# For common configuration examples, see BASIC_CONFIGURATION_README
# and STANDARD_CONFIGURATION_README. To find these documents, use
# the command "postconf html_directory readme_directory", or go to
# http://www.postfix.org/BASIC_CONFIGURATION_README.html etc.
#
# For best results, change no more than 2-3 parameters at a time,
# and test if Postfix still works after every change.
# COMPATIBILITY
#
# The compatibility_level determines what default settings Postfix
# will use for main.cf and master.cf settings. These defaults will
# change over time.
#
# To avoid breaking things, Postfix will use backwards-compatible
# default settings and log where it uses those old backwards-compatible
# default settings, until the system administrator has determined
# if any backwards-compatible default settings need to be made
# permanent in main.cf or master.cf.
#
# When this review is complete, update the compatibility_level setting
# below as recommended in the RELEASE_NOTES file.
#
# The level below is what should be used with new (not upgrade) installs.
#
compatibility_level = 3.8
# SOFT BOUNCE
#
# The soft_bounce parameter provides a limited safety net for
# testing. When soft_bounce is enabled, mail will remain queued that
# would otherwise bounce. This parameter disables locally-generated
# bounces, and prevents the SMTP server from rejecting mail permanently
# (by changing 5xx replies into 4xx replies). However, soft_bounce
# is no cure for address rewriting mistakes or mail routing mistakes.
#
#soft_bounce = no
# LOCAL PATHNAME INFORMATION
#
# The queue_directory specifies the location of the Postfix queue.
# This is also the root directory of Postfix daemons that run chrooted.
# See the files in examples/chroot-setup for setting up Postfix chroot
# environments on different UNIX systems.
#
#queue_directory = /var/spool/postfix
# The command_directory parameter specifies the location of all
# postXXX commands.
#
command_directory = /usr/sbin
# The daemon_directory parameter specifies the location of all Postfix
# daemon programs (i.e. programs listed in the master.cf file). This
# directory must be owned by root.
#
daemon_directory = /usr/lib/postfix/sbin
# The data_directory parameter specifies the location of Postfix-writable
# data files (caches, random numbers). This directory must be owned
# by the mail_owner account (see below).
#
data_directory = /var/lib/postfix
# QUEUE AND PROCESS OWNERSHIP
#
# The mail_owner parameter specifies the owner of the Postfix queue
# and of most Postfix daemon processes. Specify the name of a user
# account THAT DOES NOT SHARE ITS USER OR GROUP ID WITH OTHER ACCOUNTS
# AND THAT OWNS NO OTHER FILES OR PROCESSES ON THE SYSTEM. In
# particular, don't specify nobody or daemon. PLEASE USE A DEDICATED
# USER.
#
mail_owner = postfix
# The default_privs parameter specifies the default rights used by
# the local delivery agent for delivery to external file or command.
# These rights are used in the absence of a recipient user context.
# DO NOT SPECIFY A PRIVILEGED USER OR THE POSTFIX OWNER.
#
#default_privs = nobody
# INTERNET HOST AND DOMAIN NAMES
#
# The myhostname parameter specifies the internet hostname of this
# mail system. The default is to use the fully-qualified domain name
# from gethostname(). $myhostname is used as a default value for many
# other configuration parameters.
#
#myhostname = host.domain.tld
#myhostname = virtual.domain.tld
myhostname = mail.example.com ←mail.自分のドメイン
# The mydomain parameter specifies the local internet domain name.
# The default is to use $myhostname minus the first component.
# $mydomain is used as a default value for many other configuration
# parameters.
#
#mydomain = domain.tld
mydomain = example.com ←自分のドメイン
# SENDING MAIL
#
# The myorigin parameter specifies the domain that locally-posted
# mail appears to come from. The default is to append $myhostname,
# which is fine for small sites. If you run a domain with multiple
# machines, you should (1) change this to $mydomain and (2) set up
# a domain-wide alias database that aliases each user to
# user@that.users.mailhost.
#
# For the sake of consistency between sender and recipient addresses,
# myorigin also specifies the default domain name that is appended
# to recipient addresses that have no @domain part.
#
# Debian GNU/Linux specific: Specifying a file name will cause the
# first line of that file to be used as the name. The Debian default
# is /etc/mailname.
#
#myorigin = /etc/mailname
#myorigin = $myhostname
myorigin = $mydomain
# RECEIVING MAIL
# The inet_interfaces parameter specifies the network interface
# addresses that this mail system receives mail on. By default,
# the software claims all active interfaces on the machine. The
# parameter also controls delivery of mail to user@[ip.address].
#
# See also the proxy_interfaces parameter, for network addresses that
# are forwarded to us via a proxy or network address translator.
#
# Note: you need to stop/start Postfix when this parameter changes.
#
inet_interfaces = all
#inet_interfaces = $myhostname
#inet_interfaces = $myhostname, localhost
# The proxy_interfaces parameter specifies the network interface
# addresses that this mail system receives mail on by way of a
# proxy or network address translation unit. This setting extends
# the address list specified with the inet_interfaces parameter.
#
# You must specify your proxy/NAT addresses when your system is a
# backup MX host for other domains, otherwise mail delivery loops
# will happen when the primary MX host is down.
#
#proxy_interfaces =
#proxy_interfaces = 1.2.3.4
# The mydestination parameter specifies the list of domains that this
# machine considers itself the final destination for.
#
# These domains are routed to the delivery agent specified with the
# local_transport parameter setting. By default, that is the UNIX
# compatible delivery agent that lookups all recipients in /etc/passwd
# and /etc/aliases or their equivalent.
#
# The default is $myhostname + localhost.$mydomain + localhost. On
# a mail domain gateway, you should also include $mydomain.
#
# Do not specify the names of virtual domains - those domains are
# specified elsewhere (see VIRTUAL_README).
#
# Do not specify the names of domains that this machine is backup MX
# host for. Specify those names via the relay_domains settings for
# the SMTP server, or use permit_mx_backup if you are lazy (see
# STANDARD_CONFIGURATION_README).
#
# The local machine is always the final destination for mail addressed
# to user@[the.net.work.address] of an interface that the mail system
# receives mail on (see the inet_interfaces parameter).
#
# Specify a list of host or domain names, /file/name or type:table
# patterns, separated by commas and/or whitespace. A /file/name
# pattern is replaced by its contents; a type:table is matched when
# a name matches a lookup key (the right-hand side is ignored).
# Continue long lines by starting the next line with whitespace.
#
# See also below, section "REJECTING MAIL FOR UNKNOWN LOCAL USERS".
#
#mydestination = $myhostname, localhost.$mydomain, localhost
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
#mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain,
# mail.$mydomain, www.$mydomain, ftp.$mydomain
# REJECTING MAIL FOR UNKNOWN LOCAL USERS
#
# The local_recipient_maps parameter specifies optional lookup tables
# with all names or addresses of users that are local with respect
# to $mydestination, $inet_interfaces or $proxy_interfaces.
#
# If this parameter is defined, then the SMTP server will reject
# mail for unknown local users. This parameter is defined by default.
#
# To turn off local recipient checking in the SMTP server, specify
# local_recipient_maps = (i.e. empty).
#
# The default setting assumes that you use the default Postfix local
# delivery agent for local delivery. You need to update the
# local_recipient_maps setting if:
#
# - You define $mydestination domain recipients in files other than
# /etc/passwd, /etc/aliases, or the $virtual_alias_maps files.
# For example, you define $mydestination domain recipients in
# the $virtual_mailbox_maps files.
#
# - You redefine the local delivery agent in master.cf.
#
# - You redefine the "local_transport" setting in main.cf.
#
# - You use the "luser_relay", "mailbox_transport", or "fallback_transport"
# feature of the Postfix local delivery agent (see local(8)).
#
# Details are described in the LOCAL_RECIPIENT_README file.
#
# Beware: if the Postfix SMTP server runs chrooted, you probably have
# to access the passwd file via the proxymap service, in order to
# overcome chroot restrictions. The alternative, having a copy of
# the system passwd file in the chroot jail is just not practical.
#
# The right-hand side of the lookup tables is conveniently ignored.
# In the left-hand side, specify a bare username, an @domain.tld
# wild-card, or specify a user@domain.tld address.
#
#local_recipient_maps = unix:passwd.byname $alias_maps
#local_recipient_maps = proxy:unix:passwd.byname $alias_maps
#local_recipient_maps =
# The unknown_local_recipient_reject_code specifies the SMTP server
# response code when a recipient domain matches $mydestination or
# ${proxy,inet}_interfaces, while $local_recipient_maps is non-empty
# and the recipient address or address local-part is not found.
#
# The default setting is 550 (reject mail) but it is safer to start
# with 450 (try again later) until you are certain that your
# local_recipient_maps settings are OK.
#
unknown_local_recipient_reject_code = 550
# TRUST AND RELAY CONTROL
# The mynetworks parameter specifies the list of "trusted" SMTP
# clients that have more privileges than "strangers".
#
# In particular, "trusted" SMTP clients are allowed to relay mail
# through Postfix. See the smtpd_recipient_restrictions parameter
# in postconf(5).
#
# You can specify the list of "trusted" network addresses by hand
# or you can let Postfix do it for you (which is the default).
#
# By default (mynetworks_style = host), Postfix "trusts" only
# the local machine.
#
# Specify "mynetworks_style = subnet" when Postfix should "trust"
# SMTP clients in the same IP subnetworks as the local machine.
# On Linux, this works correctly only with interfaces specified
# with the "ifconfig" or "ip" command.
#
# Specify "mynetworks_style = class" when Postfix should "trust" SMTP
# clients in the same IP class A/B/C networks as the local machine.
# Don't do this with a dialup site - it would cause Postfix to "trust"
# your entire provider's network. Instead, specify an explicit
# mynetworks list by hand, as described below.
#
# Specify "mynetworks_style = host" when Postfix should "trust"
# only the local machine.
#
#mynetworks_style = class
#mynetworks_style = subnet
#mynetworks_style = host
# Alternatively, you can specify the mynetworks list by hand, in
# which case Postfix ignores the mynetworks_style setting.
#
# Specify an explicit list of network/netmask patterns, where the
# mask specifies the number of bits in the network part of a host
# address.
#
# You can also specify the absolute pathname of a pattern file instead
# of listing the patterns here. Specify type:table for table-based lookups
# (the value on the table right-hand side is not used).
#
#mynetworks = 168.100.3.0/28, 127.0.0.0/8
#mynetworks = $config_directory/mynetworks
#mynetworks = hash:/etc/postfix/network_table
mynetworks = 127.0.0.0/8
# The relay_domains parameter restricts what destinations this system will
# relay mail to. See the smtpd_relay_restrictions and
# smtpd_recipient_restrictions descriptions in postconf(5) for detailed
# information.
#
# By default, Postfix relays mail
# - from "trusted" clients (IP address matches $mynetworks, or is
# SASL authenticated) to any destination,
# - from "untrusted" clients to destinations that match $relay_domains or
# subdomains thereof, except addresses with sender-specified routing.
# The default relay_domains value is empty.
#
# In addition to the above, the Postfix SMTP server by default accepts mail
# that Postfix is final destination for:
# - destinations that match $inet_interfaces or $proxy_interfaces,
# - destinations that match $mydestination
# - destinations that match $virtual_alias_domains,
# - destinations that match $virtual_mailbox_domains.
# These destinations do not need to be listed in $relay_domains.
#
# Specify a list of hosts or domains, /file/name patterns or type:name
# lookup tables, separated by commas and/or whitespace. Continue
# long lines by starting the next line with whitespace. A file name
# is replaced by its contents; a type:name table is matched when a
# (parent) domain appears as lookup key.
#
# NOTE: Postfix will not automatically forward mail for domains that
# list this system as their primary or backup MX host. See the
# permit_mx_backup restriction description in postconf(5).
#
#relay_domains =
# INTERNET OR INTRANET
# The relayhost parameter specifies the default host to send mail to
# when no entry is matched in the optional transport(5) table. When
# no relayhost is given, mail is routed directly to the destination.
#
# On an intranet, specify the organizational domain name. If your
# internal DNS uses no MX records, specify the name of the intranet
# gateway host instead.
#
# In the case of SMTP, specify a domain, host, host:port, [host]:port,
# [address] or [address]:port; the form [host] turns off MX lookups.
#
# If you're connected via UUCP, see also the default_transport parameter.
#
#relayhost = $mydomain
#relayhost = [gateway.my.domain]
#relayhost = [mailserver.isp.tld]
#relayhost = uucphost
#relayhost = [an.ip.add.ress]
# REJECTING UNKNOWN RELAY USERS
#
# The relay_recipient_maps parameter specifies optional lookup tables
# with all addresses in the domains that match $relay_domains.
#
# If this parameter is defined, then the SMTP server will reject
# mail for unknown relay users. This feature is off by default.
#
# The right-hand side of the lookup tables is conveniently ignored.
# In the left-hand side, specify an @domain.tld wild-card, or specify
# a user@domain.tld address.
#
#relay_recipient_maps = hash:/etc/postfix/relay_recipients
# INPUT RATE CONTROL
#
# The in_flow_delay configuration parameter implements mail input
# flow control. This feature is turned on by default, although it
# still needs further development (it's disabled on SCO UNIX due
# to an SCO bug).
#
# A Postfix process will pause for $in_flow_delay seconds before
# accepting a new message, when the message arrival rate exceeds the
# message delivery rate. With the default 100 SMTP server process
# limit, this limits the mail inflow to 100 messages a second more
# than the number of messages delivered per second.
#
# Specify 0 to disable the feature. Valid delays are 0..10.
#
#in_flow_delay = 1s
# ADDRESS REWRITING
#
# The ADDRESS_REWRITING_README document gives information about
# address masquerading or other forms of address rewriting including
# username->Firstname.Lastname mapping.
# ADDRESS REDIRECTION (VIRTUAL DOMAIN)
#
# The VIRTUAL_README document gives information about the many forms
# of domain hosting that Postfix supports.
# "USER HAS MOVED" BOUNCE MESSAGES
#
# See the discussion in the ADDRESS_REWRITING_README document.
# TRANSPORT MAP
#
# See the discussion in the ADDRESS_REWRITING_README document.
# ALIAS DATABASE
#
# The alias_maps parameter specifies the list of alias databases used
# by the local delivery agent. The default list is system dependent.
#
# On systems with NIS, the default is to search the local alias
# database, then the NIS alias database. See aliases(5) for syntax
# details.
#
# If you change the alias database, run "postalias /etc/aliases" (or
# wherever your system stores the mail alias file), or simply run
# "newaliases" to build the necessary DBM or DB file.
#
# It will take a minute or so before changes become visible. Use
# "postfix reload" to eliminate the delay.
#
#alias_maps = dbm:/etc/aliases
#alias_maps = hash:/etc/aliases
#alias_maps = hash:/etc/aliases, nis:mail.aliases
#alias_maps = netinfo:/aliases
# The alias_database parameter specifies the alias database(s) that
# are built with "newaliases" or "sendmail -bi". This is a separate
# configuration parameter, because alias_maps (see above) may specify
# tables that are not necessarily all under control by Postfix.
#
#alias_database = dbm:/etc/aliases
#alias_database = dbm:/etc/mail/aliases
#alias_database = hash:/etc/aliases
#alias_database = hash:/etc/aliases, hash:/opt/majordomo/aliases
# ADDRESS EXTENSIONS (e.g., user+foo)
#
# The recipient_delimiter parameter specifies the separator between
# user names and address extensions (user+foo). See canonical(5),
# local(8), relocated(5) and virtual(5) for the effects this has on
# aliases, canonical, virtual, relocated and .forward file lookups.
# Basically, the software tries user+foo and .forward+foo before
# trying user and .forward.
#
#recipient_delimiter = +
# DELIVERY TO MAILBOX
#
# The home_mailbox parameter specifies the optional pathname of a
# mailbox file relative to a user's home directory. The default
# mailbox file is /var/spool/mail/user or /var/mail/user. Specify
# "Maildir/" for qmail-style delivery (the / is required).
#
#home_mailbox = Mailbox
#home_mailbox = Maildir/
# The mail_spool_directory parameter specifies the directory where
# UNIX-style mailboxes are kept. The default setting depends on the
# system type.
#
#mail_spool_directory = /var/mail
#mail_spool_directory = /var/spool/mail
# The mailbox_command parameter specifies the optional external
# command to use instead of mailbox delivery. The command is run as
# the recipient with proper HOME, SHELL and LOGNAME environment settings.
# Exception: delivery for root is done as $default_user.
#
# Other environment variables of interest: USER (recipient username),
# EXTENSION (address extension), DOMAIN (domain part of address),
# and LOCAL (the address localpart).
#
# Unlike other Postfix configuration parameters, the mailbox_command
# parameter is not subjected to $parameter substitutions. This is to
# make it easier to specify shell syntax (see example below).
#
# Avoid shell meta characters because they will force Postfix to run
# an expensive shell process. Procmail alone is expensive enough.
#
# IF YOU USE THIS TO DELIVER MAIL SYSTEM-WIDE, YOU MUST SET UP AN
# ALIAS THAT FORWARDS MAIL FOR ROOT TO A REAL USER.
#
#mailbox_command = /usr/bin/procmail
#mailbox_command = /usr/bin/procmail -a "$EXTENSION"
# The mailbox_transport specifies the optional transport in master.cf
# to use after processing aliases and .forward files. This parameter
# has precedence over the mailbox_command, fallback_transport and
# luser_relay parameters.
#
# Specify a string of the form transport:nexthop, where transport is
# the name of a mail delivery transport defined in master.cf. The
# :nexthop part is optional. For more details see the sample transport
# configuration file.
#
# NOTE: if you use this feature for accounts not in the UNIX password
# file, then you must update the "local_recipient_maps" setting in
# the main.cf file, otherwise the SMTP server will reject mail for
# non-UNIX accounts with "User unknown in local recipient table".
#
# Cyrus IMAP over LMTP. Specify ``lmtpunix cmd="lmtpd"
# listen="/var/imap/socket/lmtp" prefork=0'' in cyrus.conf.
#mailbox_transport = lmtp:unix:/var/imap/socket/lmtp
#
# Cyrus IMAP via command line. Uncomment the "cyrus...pipe" and
# subsequent line in master.cf.
#mailbox_transport = cyrus
# The fallback_transport specifies the optional transport in master.cf
# to use for recipients that are not found in the UNIX passwd database.
# This parameter has precedence over the luser_relay parameter.
#
# Specify a string of the form transport:nexthop, where transport is
# the name of a mail delivery transport defined in master.cf. The
# :nexthop part is optional. For more details see the sample transport
# configuration file.
#
# NOTE: if you use this feature for accounts not in the UNIX password
# file, then you must update the "local_recipient_maps" setting in
# the main.cf file, otherwise the SMTP server will reject mail for
# non-UNIX accounts with "User unknown in local recipient table".
#
#fallback_transport = lmtp:unix:/file/name
#fallback_transport = cyrus
#fallback_transport =
# The luser_relay parameter specifies an optional destination address
# for unknown recipients. By default, mail for unknown@$mydestination,
# unknown@[$inet_interfaces] or unknown@[$proxy_interfaces] is returned
# as undeliverable.
#
# The following expansions are done on luser_relay: $user (recipient
# username), $shell (recipient shell), $home (recipient home directory),
# $recipient (full recipient address), $extension (recipient address
# extension), $domain (recipient domain), $local (entire recipient
# localpart), $recipient_delimiter. Specify ${name?value} or
# ${name:value} to expand value only when $name does (does not) exist.
#
# luser_relay works only for the default Postfix local delivery agent.
#
# NOTE: if you use this feature for accounts not in the UNIX password
# file, then you must specify "local_recipient_maps =" (i.e. empty) in
# the main.cf file, otherwise the SMTP server will reject mail for
# non-UNIX accounts with "User unknown in local recipient table".
#
#luser_relay = $user@other.host
#luser_relay = $local@other.host
#luser_relay = admin+$local
# JUNK MAIL CONTROLS
#
# The controls listed here are only a very small subset. The file
# SMTPD_ACCESS_README provides an overview.
# The header_checks parameter specifies an optional table with patterns
# that each logical message header is matched against, including
# headers that span multiple physical lines.
#
# By default, these patterns also apply to MIME headers and to the
# headers of attached messages. With older Postfix versions, MIME and
# attached message headers were treated as body text.
#
# For details, see "man header_checks".
#
#header_checks = regexp:/etc/postfix/header_checks
# FAST ETRN SERVICE
#
# Postfix maintains per-destination logfiles with information about
# deferred mail, so that mail can be flushed quickly with the SMTP
# "ETRN domain.tld" command, or by executing "sendmail -qRdomain.tld".
# See the ETRN_README document for a detailed description.
#
# The fast_flush_domains parameter controls what destinations are
# eligible for this service. By default, they are all domains that
# this server is willing to relay mail to.
#
#fast_flush_domains = $relay_domains
# SHOW SOFTWARE VERSION OR NOT
#
# The smtpd_banner parameter specifies the text that follows the 220
# code in the SMTP server's greeting banner. Some people like to see
# the mail version advertised. By default, Postfix shows no version.
#
# You MUST specify $myhostname at the start of the text. That is an
# RFC requirement. Postfix itself does not care.
#
#smtpd_banner = $myhostname ESMTP $mail_name
#smtpd_banner = $myhostname ESMTP $mail_name ($mail_version)
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
# PARALLEL DELIVERY TO THE SAME DESTINATION
#
# How many parallel deliveries to the same user or domain? With local
# delivery, it does not make sense to do massively parallel delivery
# to the same user, because mailbox updates must happen sequentially,
# and expensive pipelines in .forward files can cause disasters when
# too many are run at the same time. With SMTP deliveries, 10
# simultaneous connections to the same domain could be sufficient to
# raise eyebrows.
#
# Each message delivery transport has its XXX_destination_concurrency_limit
# parameter. The default is $default_destination_concurrency_limit for
# most delivery transports. For the local delivery agent the default is 2.
#local_destination_concurrency_limit = 2
#default_destination_concurrency_limit = 20
# DEBUGGING CONTROL
#
# The debug_peer_level parameter specifies the increment in verbose
# logging level when an SMTP client or server host name or address
# matches a pattern in the debug_peer_list parameter.
#
#debug_peer_level = 2
# The debug_peer_list parameter specifies an optional list of domain
# or network patterns, /file/name patterns or type:name tables. When
# an SMTP client or server host name or address matches a pattern,
# increase the verbose logging level by the amount specified in the
# debug_peer_level parameter.
#
#debug_peer_list = 127.0.0.1
#debug_peer_list = some.domain
# The debugger_command specifies the external command that is executed
# when a Postfix daemon program is run with the -D option.
#
# Use "command .. & sleep 5" so that the debugger can attach before
# the process marches on. If you use an X-based debugger, be sure to
# set up your XAUTHORITY environment variable before starting Postfix.
#
debugger_command =
PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin
ddd $daemon_directory/$process_name $process_id & sleep 5
# If you can't use X, use this to capture the call stack when a
# daemon crashes. The result is in a file in the configuration
# directory, and is named after the process name and the process ID.
#
# debugger_command =
# PATH=/bin:/usr/bin:/usr/local/bin; export PATH; (echo cont;
# echo where) | gdb $daemon_directory/$process_name $process_id 2>&1
# >$config_directory/$process_name.$process_id.log & sleep 5
#
# Another possibility is to run gdb under a detached screen session.
# To attach to the screen session, su root and run "screen -r
# <id_string>" where <id_string> uniquely matches one of the detached
# sessions (from "screen -list").
#
# debugger_command =
# PATH=/bin:/usr/bin:/sbin:/usr/sbin; export PATH; screen
# -dmS $process_name gdb $daemon_directory/$process_name
# $process_id & sleep 1
# INSTALL-TIME CONFIGURATION INFORMATION
#
# The following parameters are used when installing a new Postfix version.
#
# sendmail_path: The full pathname of the Postfix sendmail command.
# This is the Sendmail-compatible mail posting interface.
#
sendmail_path = /usr/sbin/sendmail.postfix
# newaliases_path: The full pathname of the Postfix newaliases command.
# This is the Sendmail-compatible command to build alias databases.
#
newaliases_path = /usr/bin/newaliases.postfix
# mailq_path: The full pathname of the Postfix mailq command. This
# is the Sendmail-compatible mail queue listing command.
#
mailq_path = /usr/bin/mailq.postfix
# setgid_group: The group for mail submission and queue management
# commands. This must be a group name with a numerical group ID that
# is not shared with other accounts, not even with the Postfix account.
#
setgid_group = postdrop
# html_directory: The location of the Postfix HTML documentation.
#
html_directory = /usr/share/doc/postfix/html
# manpage_directory: The location of the Postfix on-line manual pages.
#
manpage_directory = /usr/share/man
# sample_directory: The location of the Postfix sample configuration files.
# This parameter is obsolete as of Postfix 2.1.
#
sample_directory = /usr/share/doc/postfix/samples
# readme_directory: The location of the Postfix README files.
#
readme_directory = /usr/share/doc/postfix/README_FILES
inet_protocols = ipv4セキュリティーとしてSASL (Simple Authentication and Security Layer)認証の導入
SMTP認証は、メールを送信する際に使用するプロトコル（SMTP）において、送信者がメールサーバーに対して自身の身元を証明するためのプロセスです。ユーザー名とパスワードを用いて認証を行うことで、メールサーバーは正当なユーザーからのメール送信を許可し、不正アクセスやスパム送信を防ぎます。
SASLは、ネットワークセキュリティプロトコルであり、データ通信中の認証とデータ保護を提供します。
# apt -y install sasl2-bin
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
db-util db5.3-util
The following NEW packages will be installed:
db-util db5.3-util sasl2-bin
0 upgraded, 3 newly installed, 0 to remove and 35 not upgraded.
Need to get 168 kB of archives.
After this operation, 706 kB of additional disk space will be used.
Get:1 http://nova.clouds.archive.ubuntu.com/ubuntu noble/main amd64 db5.3-util amd64 5.3.28+dfsg2-7 [71.7 kB]
Get:2 http://nova.clouds.archive.ubuntu.com/ubuntu noble/main amd64 db-util all 1:5.3.21ubuntu2 [2412 B]
Get:3 http://nova.clouds.archive.ubuntu.com/ubuntu noble/main amd64 sasl2-bin amd64 2.1.28+dfsg1-5ubuntu3 [94.3 kB]
Fetched 168 kB in 1s (116 kB/s)
Preconfiguring packages ...
Selecting previously unselected package db5.3-util.
(Reading database ... 106726 files and directories currently installed.)
Preparing to unpack .../db5.3-util_5.3.28+dfsg2-7_amd64.deb ...
Unpacking db5.3-util (5.3.28+dfsg2-7) ...
Selecting previously unselected package db-util.
Preparing to unpack .../db-util_1%3a5.3.21ubuntu2_all.deb ...
Unpacking db-util (1:5.3.21ubuntu2) ...
Selecting previously unselected package sasl2-bin.
Preparing to unpack .../sasl2-bin_2.1.28+dfsg1-5ubuntu3_amd64.deb ...
Unpacking sasl2-bin (2.1.28+dfsg1-5ubuntu3) ...
Setting up db5.3-util (5.3.28+dfsg2-7) ...
Setting up db-util (1:5.3.21ubuntu2) ...
Setting up sasl2-bin (2.1.28+dfsg1-5ubuntu3) ...
saslauthd.service is a disabled or a static unit, not starting it.
Processing triggers for man-db (2.12.0-4build2) ...
Scanning processes...
Scanning candidates...
Scanning linux images...
Pending kernel upgrade!
Running kernel version:
6.8.0-31-generic
Diagnostics:
The currently running kernel version is not the expected kernel version
6.8.0-36-generic.
Restarting the system to load the new kernel will not be handled automatically,
so you should consider rebooting.
Restarting services...
Service restarts being deferred:
/etc/needrestart/restart.d/dbus.service
systemctl restart getty@tty1.service
systemctl restart serial-getty@ttyS0.service
systemctl restart systemd-logind.service
systemctl restart unattended-upgrades.service
No containers need to be restarted.
No user sessions are running outdated binaries.
No VM guests are running outdated hypervisor (qemu) binaries on this host.SMTP認証の設定
SASL (Simple Authentication and Security Layer) を使った認証リクエストを処理するデーモンであるsaslauthdの設定を編集します。
viを使って編集します。
# vi /etc/default/saslauthd追加内容は以下2点です。（下の赤字部分）
START=yes追加
OPTIONS=”-c -m /var/spool/postfix/var/run/saslauthd”に変更
#
# Settings for saslauthd daemon
# Please read /usr/share/doc/sasl2-bin/README.Debian.gz for details.
#
START=yes
# Description of this saslauthd instance. Recommended.
# (suggestion: SASL Authentication Daemon)
DESC="SASL Authentication Daemon"
# Short name of this saslauthd instance. Strongly recommended.
# (suggestion: saslauthd)
NAME="saslauthd"
# Which authentication mechanisms should saslauthd use? (default: pam)
#
# Available options in this Debian package:
# getpwent -- use the getpwent() library function
# kerberos5 -- use Kerberos 5
# pam -- use PAM
# rimap -- use a remote IMAP server
# shadow -- use the local shadow password file
# sasldb -- use the local sasldb database file
# ldap -- use LDAP (configuration is in /etc/saslauthd.conf)
#
# Only one option may be used at a time. See the saslauthd man page
# for more information.
#
# Example: MECHANISMS="pam"
MECHANISMS="pam"
# Additional options for this mechanism. (default: none)
# See the saslauthd man page for information about mech-specific options.
MECH_OPTIONS=""
# How many saslauthd processes should we run? (default: 5)
# A value of 0 will fork a new process for each connection.
THREADS=5
# Other options (default: -c -m /var/run/saslauthd)
# Note: You MUST specify the -m option or saslauthd won't run!
#
# WARNING: DO NOT SPECIFY THE -d OPTION.
# The -d option will cause saslauthd to run in the foreground instead of as
# a daemon. This will PREVENT YOUR SYSTEM FROM BOOTING PROPERLY. If you wish
# to run saslauthd in debug mode, please run it by hand to be safe.
#
# See the saslauthd man page and the output of 'saslauthd -h' for general
# information about these options.
#
# Example for chroot Postfix users: "-c -m /var/spool/postfix/var/run/saslauthd"
# Example for non-chroot Postfix users: "-c -m /var/run/saslauthd"
#
# To know if your Postfix is running chroot, check /etc/postfix/master.cf.
# If it has the line "smtp inet n - y - - smtpd" or "smtp inet n - - - - smtpd"
# then your Postfix is running in a chroot.
# If it has the line "smtp inet n - n - - smtpd" then your Postfix is NOT
# running in a chroot.
#OPTIONS="-c -m /var/run/saslauthd"
OPTIONS=-c -m /var/spool/postfix/var/run/saslauthdPostfixの起動
# systemctl start postfix起動時のPostfix実行
サーバー起動時に自動実行させるようにします。
# systemctl enable postfix
Synchronizing state of postfix.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install enable postfixポートの開放
SMTPとしてポート25を開放します。
# ufw allow 25/tcp
Rule added
Rule added (v6)telnetによるメール送信テスト
telnetを利用して、メールが送信できるかテストしてみます。
対話型になるので、赤文字のコメントを参考にしながら青文字部分を入力してください。
# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 mail.example.com ESMTP Postfix
HELO localhost
250 mail.example.com
MAIL FROM:your-email@example.com ←送信元
250 2.1.0 Ok
RCPT TO:recipient@example.com ←送信先
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
Subject: Test Mail ←タイトル
This is a test email. ←本文
. ←ピリオドで終了
250 2.0.0 Ok: queued as 12345
QUIT ←Telnetの終了
221 2.0.0 Bye
Connection closed by foreign host.これで送信先にテストメールが届いていれば、SMTPサーバー構築の完了です。
ご覧いただき有難うございました。良かったら いいね(thumb up)ボタンをお願いします。
PR
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