在学习服务器监控的发现mail无法发送邮件到邮箱，百度之后发现是阿里云将25好端口禁用，改为使用465端口，所以大概记录一下
环境：阿里云、Centos7 x64 邮箱：163邮箱
163邮箱开启smtp服务、客户端授权密码
安装对应软件包
yum install -y sendmail xmail
下载证书
#创建证书存放文件
mkdir ~/.certs
#生产证书
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/mail.crt
certutil -A -n "GeoTrust Global CA" -t "C,," -d ~/.certs -i ~/.certs/mail.crt
certutil -A -n "GeoTrust SSL CA - G3" -t "Pu,Pu,Pu" -d ~/.certs -i ~/.certs/mail.crt
#查看证书
certutil -A -n "GeoTrust SSL CA - G3" -t "Pu,Pu,Pu" -d ./ -i ~/.certs/163.crt
修改mail配置文件
#vim /etc/mail.rc
#在文件最后添加
set from=xxxx@163.com
set smtp=smtps://smtp.163.com:465
set smtp-auth-user=xxxx@163.com
set smtp-auth-password=PASSWORD
set smtp-auth=login
set ssl-verify=ignore
set nss-config-dir=/root/.certs
启动mail服务
systemctl start sendmail
systemctl enable sendmail
错误：My unqualified host name(...) unknow
