本次测试版本：centos7.6

第一步安装mailx
 

yum install mailx

安装结果如下：

[root@CentOS764 ~]# yum install mailx
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
epel/x86_64/metalink                                                                        |  35 kB  00:00:00     * base: mirrors.aliyun.com* epel: mirror.nyist.edu.cn* extras: mirrors.aliyun.com* updates: mirrors.aliyun.com
base                                                                                        | 3.6 kB  00:00:00     
epel                                                                                        | 4.3 kB  00:00:00     
extras                                                                                      | 2.9 kB  00:00:00     
updates                                                                                     | 2.9 kB  00:00:00     
epel/x86_64/primary_db         FAILED                                          
https://ftp.kaist.ac.kr/pub/epel/7/x86_64/repodata/c791872357f7caad8e42d6043268fd6d0fadb243608366829f3097d94a7f3180-primary.sqlite.gz: [Errno 14] curl#35 - "TCP connection reset by peer"
Trying other mirror.
(1/3): epel/x86_64/updateinfo                                                               | 1.0 MB  00:00:02     
(2/3): updates/7/x86_64/primary_db                                                          |  27 MB  00:00:23     
(3/3): epel/x86_64/primary_db                                                               | 8.7 MB  00:01:37     
Resolving Dependencies
--> Running transaction check
---> Package mailx.x86_64 0:12.5-19.el7 will be installed
--> Finished Dependency ResolutionDependencies Resolved===================================================================================================================Package                  Arch                      Version                          Repository               Size
===================================================================================================================
Installing:mailx                    x86_64                    12.5-19.el7                      base                    245 kTransaction Summary
===================================================================================================================
Install  1 PackageTotal download size: 245 k
Installed size: 466 k
Is this ok [y/d/N]: y
Downloading packages:
mailx-12.5-19.el7.x86_64.rpm                                                                | 245 kB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Warning: RPMDB altered outside of yum.Installing : mailx-12.5-19.el7.x86_64                                                                        1/1 Verifying  : mailx-12.5-19.el7.x86_64                                                                        1/1 Installed:mailx.x86_64 0:12.5-19.el7                                                                                       Complete!
[root@CentOS764 ~]# 

第二步用命令打开mail配置文件

vi /etc/mail.rc

结果如下：

[root@CentOS764 etc]# vi /etc/mail.rc# See mailx(1) for further options.
# This file is not overwritten when 'make install' is run in
# the mailx build process again.# Sccsid @(#)nail.rc    2.11 (gritter) 8/2/08# Do not forward to mbox by default since this is likely to be
# irritating for most users today.
set hold# Append rather than prepend when writing to mbox automatically.
# This has no effect unless 'hold' is unset again.
set append# Ask for a message subject.
set ask# Assume a CRT-like terminal and invoke a pager.
set crt# Messages may be terminated by a dot.
set dot# Do not remove empty mail folders in the spool directory.
# This may be relevant for privacy since other users could
# otherwise create them with different permissions.
set keep# Do not remove empty private mail folders.
set emptybox# Quote the original message in replies by "> " as usual on the Internet.
set indentprefix="> "
set from=abc@163.com smtp=smtp.163.com
set smtp-auth-user=abc@163.com smtp-auth-password=123456 set smtp
-auth=login

连续按两次 i  进入编辑模式，增加如下代码后就变成上面这样

set from=abc@163.com smtp=smtp.163.com
set smtp-auth-user=abc@163.com smtp-auth-password=123456 set smtp
-auth=login

保存文件并退出：:wq