Overview
Message rewriting alters aspects of an email message as it is processed by the mail server. This can involve changing the sender or recipient addresses in the envelope (the 'outside' of the message), or modifying the content itself, including headers, body, and attachments.
Envelope
Address rewriting alters the email addresses in the envelope of a message as it passes through the mail server. The envelope, distinct from the message content, carries the routing information (sender or return path, and recipients).
Headers
Message header rewriting involves the process of adding, removing, or modifying the headers of an email message. Headers are crucial parts of an email, as they contain meta-information about the email, such as the sender, recipient, subject, and other technical details, including those required for proper routing and delivery.
Body & Attachments
Message rewriting is the process of modifying the content of the email messages as they pass through the system. This can include altering the body text of the message, adjusting or removing attachments, and other similar alterations. It's important to note that this rewriting is performed by the mail server and happens before the message is delivered to its final destination.