本文简单整理了一下如何在Linux服务器上安装、配置SendMail发送邮件的步骤，此文不是配置邮件服务器，具体测试环境为CentOS Linux release 7.2.1511 (Core) ，如遇特殊平台有所差别，请以实际情况为准则。
Linux 系统版本查看
检查、了解系统版本信息，主要是如果使用rpm安装时，需要下载合适的版本。
[root@mylnx06 ~]# more /etc/redhat-release
CentOS Linux release 7.2.1511 (Core)
检查是否安装sendmail组件
如下所示，该服务器上并没有安装sendmail的相关组件。那么我们直接使用yum安装sendmail组件即可。
[root@mylnx06 ~]# rpm -qa | grep sendmail
[root@mylnx06 ~]# yum list sendmail
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* epel: ftp.cuhk.edu.hk
Available Packages
sendmail.x86_64 8.14.7-4.el7 base
使用yum安装sendmail组件，当然你可以使用其它方式安装，此处不做展开介绍。
[root@mylnx06 ~]# yum install sendmail.x86_64
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* epel: ftp.cuhk.edu.hk
Resolving Dependencies
--> Running transaction check
---> Package sendmail.x86_64 0:8.14.7-4.el7 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
Package Arch Version Repository Size
Installing:
sendmail x86_64 8.14.7-4.el7 base 722 k
Transaction Summary
Install 1 Package
Total download size: 722 k
Installed size: 1.6 M
Is this ok [y/d/N]: y
Downloading packages:
sendmail-8.14.7-4.el7.x86_64.rpm | 722 kB 00:00:00
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : sendmail-8.14.7-4.el7.x86_64 1/1
Verifying : sendmail-8.14.7-4.el7.x86_64 1/1
Installed:
sendmail.x86_64 0:8.14.7-4.el7
Complete!
[root@mylnx06 ~]#
编辑/etc/aliases文件
Sendmail有一个非常实用的功能,就是为每个账号取别名(Aliase) 会使用一个在 /etc/aliases 中的档案做使用者名称转换的动作。 所以这个配置文件是可配也可以不配，具体视你的需求而定。
[root@mylnx06 ~]# vi /etc/aliases
#
# Aliases in this file will NOT be expanded in the header from
# Mail, but WILL be visible over networks or from /bin/mail.
#
# >>>>>>>>>> The program "newaliases" must be run after
# >> NOTE >> this file is updated for any changes to
# >>>>>>>>>> show through to sendmail.
#
# Basic system aliases -- these MUST be present.
mailer-daemon: postmaster
postmaster: root
# General redirections for pseudo accounts.
bin: root
daemon: root
adm: root
lp: root
sync: root
shutdown: root
halt: root
mail: root
news: root
uucp: root
operator: root
games: root
gopher: root
ftp: root
nobody: root
radiusd: root
nut: root
dbus: root
vcsa: root
canna: root
wnn: root
rpm: root
nscd: root
pcap: root
apache: root
webalizer: root
dovecot: root
fax: root
quagga: root
radvd: root
pvm: root
amandabackup: root
privoxy: root
ident: root
named: root
xfs: root
gdm: root
mailnull: root
postgres: root
sshd: root
smmsp: root
postfix: root
netdump: root
ldap: root
squid: root
ntp: root
mysql: root
desktop: root
rpcuser: root
rpc: root
nfsnobody: root
ingres: root
system: root
toor: root
manager: root
dumper: root
abuse: root
newsadm: news
newsadmin: news
usenet: news
ftpadm: ftp
ftpadmin: ftp
ftp-adm: ftp
ftp-admin: ftp
www: webmaster
webmaster: root
noc: root
security: root
hostmaster: root
info: postmaster
marketing: postmaster
sales: postmaster
support: postmaster
# trap decode to catch security attacks
decode: root
# Person who should get root's mail
#root: marc
如下截图所示，如果我配置别名为root的，配置接收邮件（下面邮件仅仅是一个模板而已）
修改配置文件sendmail.cf
修改/etc/mail/sendmail.cf 添加对应的DS, DS后面为邮件服务器的IP地址。根据实际具体情况配置。其实这个配置文件，如果需要，还有蛮多需要配置、细化的地方，此处只讲述最简单的配置。
# host/domain names ending with a token in class P are canonical
CP.
# "Smart" relay host (may be null)
DS[xxx.xxx.xxx.xxx]
# operators that cannot be in local usernames (i.e., network indicators)
CO @ % !
# a class with just dot (for identifying canonical names)
重启sendmail服务
[root@mylnx06 ~]# service sendmail status
Redirecting to /bin/systemctl status sendmail.service
sendmail.service - Sendmail Mail Transport Agent
Loaded: loaded (/usr/lib/systemd/system/sendmail.service; enabled; vendor preset: disabled)
Active: inactive (dead)
Feb 22 10:29:45 azlnx06 systemd[1]: Stopped Sendmail Mail Transport Agent.
[root@mylnx06 ~]# service sendmail start
Redirecting to /bin/systemctl start sendmail.service
[root@mylnx06 ~]# service sendmail status
Redirecting to /bin/systemctl status sendmail.service
sendmail.service - Sendmail Mail Transport Agent
Loaded: loaded (/usr/lib/systemd/system/sendmail.service; enabled; vendor preset: disabled)
Active: active (running) since Wed 2017-02-22 10:42:02 HKT; 5s ago
Process: 46129 ExecStart=/usr/sbin/sendmail -bd $SENDMAIL_OPTS $SENDMAIL_OPTARG (code=exited, status=0/SUCCESS)
Process: 46116 ExecStartPre=/etc/mail/make aliases (code=exited, status=0/SUCCESS)
Process: 46115 ExecStartPre=/etc/mail/make (code=exited, status=0/SUCCESS)
Main PID: 46131 (sendmail)
CGroup: /system.slice/sendmail.service
└─46131 sendmail: accepting connections
Feb 22 10:42:02 azlnx06 systemd[1]: Starting Sendmail Mail Transport Agent...
Feb 22 10:42:02 azlnx06 sendmail[46124]: alias database /etc/aliases rebuilt by root
Feb 22 10:42:02 azlnx06 sendmail[46124]: /etc/aliases: 77 aliases, longest 17 bytes, 792 bytes total
Feb 22 10:42:02 azlnx06 sendmail[46131]: starting daemon (8.14.7): SMTP+queueing@01:00:00
Feb 22 10:42:02 azlnx06 systemd[1]: PID file /run/sendmail.pid not readable (yet?) after start.
Feb 22 10:42:02 azlnx06 systemd[1]: Started Sendmail Mail Transport Agent
测试邮件服务
如下所示，使用mail命令测试能否成功收到邮件。如果成功，表示前面配置OK， 如果没有收到邮件，则必须检查日志，然后根据具体错误信息诊断问题。
[root@mylnx06 ~]# cat > test.txt
it is only test
^Z
[1]+ Stopped cat > test.txt
[root@mylnx06 ~]# mail -s "test" konglb@xxxx.com < test.txt
[root@mylnx06 ~]#
[azrlnx06azlnx06 ~]$ echo 'it is only a test' | mail -s "test eamil" konglb@xxxx.com
[azrlnx06@azlnx06 ~]$