Envelope-From

Envelope-From identifies the sender in an email’s transport envelope. It is passed using the SMTP command MAIL FROM. This reverse path serves especially as the destination for error reports; it is not equivalent to the visible sender line.

Plan the technical return route

In the fictional design, a portal sends message E-662 through an external service. The service uses a technical mailbox for bounces while the visible From field contains the portal address. The SMTP sender and visible sender can serve different purposes.

For this design, the team documents who processes the feedback and how it is linked to the right message. Changing only the visible address does not set up this return route. The transport address likewise does not replace verified user access in the portal.

Handle empty reverse paths correctly

Certain technical notifications deliberately use an empty reverse path to prevent error loops. It should therefore not be indiscriminately overwritten with a company address. Check the behaviour in the intended sending service. For business processing, what matters is which feedback returns to the application and who handles it.

Sources

• IETF: Simple Mail Transfer Protocol

• Microsoft: Email authentication