ERPnext firewall and ports

I’m about to install ERPnext behind a firewall host.

I have problems setting up E-Mail + Email-Domain as it triggers port 9000 for unknown reason …

Can someone list all firewall ports I need to open/forward to/from the ERPnext host + its purpose?

Port    | In/Out   |Protocol    | Purpose 
8000    | In       | TCP        | Website
143     | Out      | TCP        | IMAP
9000    | Out      | TCP        | ...
...     | ....     | ...        | ...

SMTP TCP 25 In and out
IMAP TCP 143 In and out

ERPnext has it’s own email server? I thought it is just mapping to an external one? Like an email client eg.

is it your own premise installation or from cloud

It is my own installation.

Having a detailed list of all ports go in and out helps running ERPnext in DMZ eg.