0.环境准备
修改hosts文件
127.0.0.1 localhost.localdomain localhost 主机名
127.0.0.1 主机名
1.需要用到的软件包：sendmail，mailx
两者直接用yum安装即可
yum -y install sendmail mailx
3.配置mailx配置文件，直接在尾部加入配置
vi /eta/mail.rc
set from=xxx@163.com #设置发件人，这个可以随意填写，建议和邮箱一致
set smtp=smtps://smtp.163.com:465
set smtp-auth-user=xxx@163.com #设置邮箱
set smtp-auth-password=xxx #设置授权码
set smtp-auth=login
set nss-config-dir=/root/.certs/
set ssl-verify=ignore
4.配置证书
mkdir -p /root/.certs/
echo -n | openssl s_client -connect smtp.163.com:465 | sed -ne \'/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p\' > ~/.certs/163.crt
certutil -A -n "GeoTrust SSL CA" -t "C,," -d ~/.certs -i ~/.certs/163.crt
certutil -A -n "GeoTrust Global CA" -t "C,," -d ~/.certs -i ~/.certs/163.crt
certutil -L -d /root/.certs
cd /root/.certs/
certutil -A -n "GeoTrust SSL CA - G3" -t "Pu,Pu,Pu" -d ./ -i 163.crt
返回如下提示即可：
Notice: Trust flag u is set automatically if the private key is present.
5.启动服务，发送邮件
systemctl start sendmail
echo 内容 | mailx -s \'标题\' 接收人邮箱
注意！！
mailx -v 选项可以查看执行过程，对排错很有用！