Remove Private IP Address of Client From Email Header

[Offroad]

Yes, from the thread you referenced:

@wolf1

Thunderbird can be configured to hide the LAN-IP or to provide a fake-IP. Just edit mail.smtpserver.default.hello_argument to localhost and within the extended HELO the client (eg Tunderbird) provides “localhost” to the Server.

In addition, the final post of the thread demonstrates that RFC 5321 indicates hosts should be known by names and not numerical addresses:

@wolf1

For the purposes of this specification, a host is a computer system
attached to the Internet (or, in some cases, to a private TCP/IP
network) and supporting the SMTP protocol. Hosts are known by names
(see the next section); they SHOULD NOT be identified by numerical
addresses, i.e., by address literals as described in

{Section 4.1.2}