$ sudo apt install sendmail mailutils sendmail-bin
$ sudo nano /etc/hosts
Install
# apt install sendmail
# apt install m4
# apt install sendmail-cf
修改 nano /etc/mail/sendmail.mc 約116行，把127.0.0.1改為0.0.0.0
DAEMON_OPTIONS(`Port=smtp,Addr=0.0.0.0, Name=MTA')dnl
編碼
# m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
4. 重啟sendmail
# systemctl restart sendmail
# systemctl status sendmail
5. 查看是否有啟動
# netstat -at | grep smtp
tcp 0 0 *:smtp *:* LISTEN