Dianne Skoll via linux wrote on 2026-09-22 14:15:
Still, Gmail discloses your IP address to your e-mail recipient,
which is not that good when you send something to mailing list like
this:
Don't all SMTP servers do that? Adding a Received: header is a MUST
requirement in RFC 5321 (though inclusion of the IP address is only a
SHOULD): https://www.rfc-editor.org/info/rfc5321/#section-4.4
I had to do a test to verify that Gmail was doing that, and it does
include my home IP address.
As you say, it should, but I think when using web mail (and/or the app?)
it does not do that.
I've added to my /etc/postfix/master.cf:
submission_hide_home_ip unix n - n - 0 cleanup
-o header_checks=pcre:/etc/postfix/submission_hide_home_ip.pcre
and my /etc/postfix/submission_hide_home_ip.pcre:
/^(Received: from ).*\([0-9\.\-]+cable.teksavvy.com.*\)(.*by .*)$/AU
REPLACE ${1}***ISP name hidden*** ${2}
For fixing this exact issue.
A received message header now shows:
Received: from ***ISP name hidden***
by mail.bclug.ca (Postfix) with ESMTPSA id E771F81BB4
for<linux [ at ] linux-ottawa [ dot ] org>; Tue, 22 Sep 2026 14:04:20 -0700 (PDT)