Return-Path: <existing@bar.com>
From: Foo Bar <existing@bar.com>
To: category@bar.com
Subject: This is a topic from an existing user
Date: Fri, 15 Jan 2016 00:12:43 +0100
Message-ID: <32@foo.bar.mail>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Authentication-Results: example.com; dmarc=fail

Hey, this is a topic from an existing user ;)