The Mail From (MFrom) address is the email address that identifies from where the email actually came. It is automatically added to the envelope of the message by the sending mail transfer agent (MTA) before the message is sent. The MFrom is the address to which undeliverable message notices, or bounces, are sent.
The MFrom address is also referred to as:
- The Return-Path address
- The Envelope-Sender address
- The bounce address
