本文介绍如何在用Postfix 和Dovecot 在CentOS 6 上搭建一个 POP3/IMAP/SMTP 邮件服务器。你可能不知道啥子是Postfix，这货是Sendmail的完美替代品，sendmail不但发信慢，而且还容易堆积一堆邮件，消耗服务器资源。Postfix不但速度快，而且容易管理，还更安全。

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升级系统

screen -U -S mailserver-screen
yum update

创建用户组

groupadd vmail -g 2222

创建用户

useradd vmail -r -g 2222 -u 2222 -d /var/vmail -m -c "mail user"

安装Postfix

yum remove exim sendmail
yum install postfix cronie

修改postfix 配置文件 main.cf

cp /etc/postfix/main.cf{,.orig}
vim /etc/postfix/main.cf

myhostname = fatesinger.com
mydomain = fatesinger.com
myorigin = $mydomain
queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
mail_owner = postfix
unknown_local_recipient_reject_code = 550
alias_maps = hash:/etc/postfix/aliases
alias_database = $alias_maps
inet_interfaces = all
inet_protocols = ipv4
mydestination = $myhostname, localhost.$mydomain, localhost
debug_peer_level = 2
debugger_command =
PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin ddd $daemon_directory/$process_name $process_id & sleep 5
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
setgid_group = postdrop
html_directory = no
manpage_directory = /usr/share/man
sample_directory = /usr/share/doc/postfix-2.6.6/samples
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
relay_domains = *
virtual_alias_maps=hash:/etc/postfix/vmail_aliases
virtual_mailbox_domains=hash:/etc/postfix/vmail_domains
virtual_mailbox_maps=hash:/etc/postfix/vmail_mailbox
virtual_mailbox_base = /var/vmail
virtual_minimum_uid = 2222
virtual_transport = virtual
virtual_uid_maps = static:2222
virtual_gid_maps = static:2222
smtpd_sasl_auth_enable = yes
smtpd_sasl_type = dovecot
smtpd_sasl_path = /var/run/dovecot/auth-client
smtpd_sasl_security_options = noanonymous
smtpd_sasl_tls_security_options = $smtpd_sasl_security_options
smtpd_sasl_local_domain = $mydomain
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination

创建vmail_domains配置文件

vim /etc/postfix/vmail_domains

mydomain.com            OK
my-otherdomain.com      OK

创建vmail_mailbox配置文件

vim /etc/postfix/vmail_mailbox

info@mydomain.com           mydomain.com/info/
info@my-otherdomain.com     my-otherdomain.com/info/

创建vmail_aliases配置文件

vim /etc/postfix/vmail_aliases

info@mydomain.com           info@mydomain.com
info@my-otherdomain.com     foo@bar.tld

hash 配置文件

postmap /etc/postfix/vmail_domains
postmap /etc/postfix/vmail_mailbox
postmap /etc/postfix/vmail_aliases

touch /etc/postfix/aliases
vim +/submission /etc/postfix/master.cf

submission inet n       -       n       -       -       smtpd

安装DOVECOT

yum install dovecot

修改dovecot的配置文件dovecot.conf

cp /etc/dovecot/dovecot.conf{,.orig}
vim /etc/dovecot/dovecot.conf

listen = *
ssl = no
protocols = imap lmtp
disable_plaintext_auth = no
auth_mechanisms = plain login
mail_access_groups = vmail
default_login_user = vmail
first_valid_uid = 2222
first_valid_gid = 2222
#mail_location = maildir:~/Maildir
mail_location = maildir:/var/vmail/%d/%n

passdb {
    driver = passwd-file
    args = scheme=SHA1 /etc/dovecot/passwd
}
userdb {
    driver = static
    args = uid=2222 gid=2222 home=/var/vmail/%d/%n allow_all_users=yes
}
service auth {
    unix_listener auth-client {
        group = postfix
        mode = 0660
        user = postfix
    }
    user = root
}
service imap-login {
  process_min_avail = 1
  user = vmail
}

创建虚拟用户的密码文件。用户名和密码会储存在这里。

touch /etc/dovecot/passwd
doveadm pw -s sha1 | cut -d '}' -f2

vim /etc/dovecot/passwd

info@mydomain.com:DOzcsKI8HY0bg8LAuz0DPKwS3WA=

chown root: /etc/dovecot/passwd
chmod 600 /etc/dovecot/passwd

启动服务

chkconfig postfix on
chkconfig dovecot on
service postfix restart
service dovecot restart

如果是centos7 则使用如下命令

systemctl enable postfix.service
systemctl enable dovecot.service
systemctl start  postfix.service
systemctl start  dovecot.service

之后就可以测试收发邮件了。