Note: This is a different request than the similar SMTP Token customization.

Problem Statement

Currently, Proton Mail (including Proton Bridge) uses the same authentication credentials for both receiving and sending email. This creates a security risk when integrating third-party services:

Single Point of Failure: Any service with my credentials can send emails from my account
No Safe-by-Design Option: Even if I instruct an AI agent not to send, there's no technical enforcement
Least-Privilege Violation: Services that only need to read/process mail shouldn't have send capability

Use Cases

AI Email Assistants: Sort, prioritize, summarize incoming mail without send risk
Automation Scripts: Process incoming mail for workflows (e.g., ticket creation, notifications)
Third-Party Filters: Advanced spam filtering, categorization services
Backup Solutions: Secure mail archiving without send capability

Greatest security threat is AI agents. Handing the ability to read emails to an agent automatically allows it access to sending mail as well. AI agents should not be able to access SMTP and admin panels just with the credentials to read email.

Quick test implementation opportunity: Implement it in Proton Mail Bridge first. This should be a relatively minor update without impacting the general Protonmail service.