I am trying to use a Sieve filter to move emails to a folder based on the content of the email body. For example, I want a filter that moves emails containing the phrase "Thank you for submitting a bug report to Vivaldi" into my Archive folder.

Currently, when I add this to my Sieve script:

require ["fileinto", "imap4flags", "body"];

if body :text :contains "Thank you for submitting a bug report to Vivaldi" {
fileinto "Archive";
addflag "\Seen";
}

I receive the error: unexpected identifier: body

This indicates that the body extension is not supported in ProtonMail Sieve, although it is defined in RFC 5228 / RFC 5238
as an optional Sieve extension.

Expected behavior:

ProtonMail should support the body extension so that users can filter emails based on the content of the message body.

Alternatively, a note in the documentation stating that body is not supported would help.

Impact:

Currently, filtering based on message content is impossible, limiting the ability to automate inbox management.

Users have to rely on Subject, From, To, or flags only.

Also built-in wizard has no body selection.