I just sent my first email using the Mail app through a fully functional email Postfix+Dovecot server.
I am worried by the fact that it also sends my IP address and hostname along with it.
The header that is causing this is
Received: from mycomp-mbp.domain_not_set.invalid (cpe-IP-HERE.dynamic.ISPHERE.net [IPHERE]) by mydomain.com (Postfix) with ESMTPSA id 70F1D1B459 for <firstname.lastname@example.org>; Fri, 1 Feb 2019 11:17:45 +0100 (CET)
How can I instruct Mail app to not send this information along the way?