The key differences between the Mail From (MFrom) address and the From address include:
- The sending domain of the From address might not be the same as the Mail From (MFrom) domain depending on your sending practices.
- During authentication, Sender Policy Framework (SPF) checks the domain in the MFrom address, not the From address domain.
- The MFrom address is where SMTP error messages (bounce messages) are sent.
- Both addresses can be found in separate locations in the email header, as shown in an example below.
The MFrom address is also referred to as the Return-Path address, Envelope-Sender address, and the bounce address.
Header Example
X-Apparently-To: example@exampledomain.com; Wed, 20 Jan 2016 11:11:10 +0000
Return-Path: <bounce@example.net>
Received-SPF: pass (domain of example.net designates XX.XX.XXX.XXX as permitted sender)
MIME-Version: 1.0
Content-Disposition: inline
Content-Transfer-Encoding: binary
Content-Type: text/html; charset=utf-8
X-Mailer: MIME::Lite 3.027 (F2.74; A2.03; B3.07; Q3.07)
Date: Wed, 20 Jan 2016 04:11:09 -0700
From: ABC Company <assurance@abccompany.net>
Reply-To: ABC Company <marketing@abccompany.net>
To: example@exampledomain.com
Subject: Here's why your mail is getting filtered...
X-Rpaspmid: 1453288262
X-Rptags: Newsletter 1453288262
Message-Id: <20160120111109.BFB1E7E004@tools-d1.lan.abccompany.net>
Content-Length: 14716
