digitalocean install Mail-in-a-Box

create droplet

install:

curl -s https://mailinabox.email/setup.sh | sudo bash

reverse DNS:

Clidk droplet -> your droplet name -> Setting -> Rename

the new name must be "demo.com"

important thing is ----> we MUST WAIT for DNS update.

SMTP port 25  blocked：

On some new accounts port 25 may be blocked by default. This block can be lifted as long as your account has no history of abuse by opening a ticket with our support team from the control panel or by emailingsupport@. They will verify for you whether a block is in place and can remove it if one is present.

SSL 

https://www.pianyissl.com

get the zip, use ALL

TLS (SSL) Certificates

修改/home/user-data/ssl/ssl_private_key.pem.