0. 환경
sendmail 8.15.2
dovecot 2.2.36
let's encrypt 인증서 사용
1. /etc/mail/sendmail.cf 수정
CACertPath=/etc/letsencrypt/live/mail.yeonghoon.kim
CACertFile=/etc/letsencrypt/live/mail.yeonghoon.kim/chain.pem
ServerCertFile=/etc/letsencrypt/live/mail.yeonghoon.kim/cert.pem
ServerKeyFile=/etc/letsencrypt/live/mail.yeonghoon.kim/privkey.pem
2. /etc/dovecot/conf.d/10-ssl.conf 수정
ssl = yes
ssl_cert = </etc/letsencrypt/live/mail.yeonghoon.kim/cert.pem
ssl_key = </etc/letsencrypt/live/mail.yeonghoon.kim/privkey.pem
ssl_ca = </etc/letsencrypt/live/mail.yeonghoon.kim/chain.pem
3. 데몬 재구동
systemctl restart sendmail.service
systemctl restart dovecot.service