Currently, Sieve filters in Proton Mail are limited to basic actions such as sorting, discarding, or moving messages, and the built-in autoresponder only supports static replies. For many business and professional use cases, it would be extremely valuable if Proton Mail supported:

1. The Sieve vacation extension (RFC 5230), which enables automatic replies to incoming emails.

2. The Sieve variables extension (RFC 5229), which allows dynamic insertion of values (such as the sender’s address, subject line, or other header fields) into the auto-reply message.

With these two extensions, users could create more powerful and personalized auto-replies, for example:

Confirming receipt of a support request and including the sender’s email in the response.

Sending conditional auto-replies based on recipient address or subject line.

Implementing lightweight ticket acknowledgment systems without requiring third-party integrations.

Would Proton Mail consider implementing support for these extensions in the future? This would greatly improve flexibility and make Proton Mail more useful for professional communication scenarios.