Currently, Proton SMTP requires the Return-Path (envelope sender) to match the authenticated sending address. This makes it impossible to use dedicated bounce addresses such as bounce@domain.com, which are required by many business applications, including Odoo, CRM systems, ticketing platforms, and newsletter tools.

Please add support for a custom Return-Path / envelope sender while still enforcing that the domain belongs to a verified Proton Mail domain. This would enable proper bounce processing, DMARC-compliant email workflows, and integration with common business software without requiring external SMTP relay services.

This feature would significantly improve Proton Mail's suitability as a business email platform.