User Story: As I process my INBOX, adding Labels to categorise my emails, I want a filter to be triggered manually or recurrently, which take certain actions on the emails in the INBOX, based on how I have manually - or automatically - labelled those emails.

This was possible, using a client like Thunderbird, against an IMAP server - maybe 7 years ago; it was frustrating to realise, that this was not at all built into the web GUI and server implementation of proton email.

I've tried sieve filters, ex. if hasflag ["labelname", "\\labelname", "Labelname", "\\Labelname"] in the filter, and have applied the label "labelname" to the emails - but obviously hasflag has nothing to do with labels or folders, nor is there anything in the documentation hinting on how to create a filter that reacts on a specific folder or label.

• Since flags are part of sieve RFC, could that be used to do server side filtering on tags implemented as IMAP4 flags; or is the issue here the risks of server side cyclic filter implementations?

It would be nice to have this feature on the server side, so that we could use it across platforms - ie. a user can tag stuff with labels from a handheld device, using the proton mail client application, and it would work the same way as on a laptop with another mail client; noted that thunderbird is available as a mail client on android systems - ill get back to this idea if I find a solution working for this use case.