iRedMail 使用自有证书
mv /etc/ssl/certs/iRedMail.crt{,.bak} #备份iRedMail.crt为 iRedMail.crt.bak
mv /etc/ssl/private/iRedMail.key{,.bak} # 备份 iRedMail.key 为iRedMail.key.bak
cp 123.crt /etc/ssl/certs/iRedMail.crt #重名上传即可
cp 123.pem /etc/ssl/private/iRedMail.key