It would be greatly appreciated if there was the ability to filter existing emails based on environment with a custom sieve filter. There are a number of reasons why this could benefit everyone trying to organize their emails as they adapt into Proton Mail.

Here are my issues with not having this ability:

Importing a large batch of emails with Easy Switch usually calls for manually applying filters to existing mail.
This means all my emails in the trash are relabeled and clutter my label filters. I now have to either delete the trash permanently or move the emails out and back into the trash to remove the labels again.

This problem extends to my archived mail. I don't want to relabel them after they have just been sorted into the archive. Not having the ability to avoid labeling these adds them back into the "unarchived" labels I just removed.

I know that this is possible because it is provided by default to avoid the spam inbox. This concept should really be expanded upon.

environment :matches "vnd.proton.spam-threshold" "*",

spamtest :value "ge" :comparator "i;ascii-numeric" "${1}"

Some extra details, I don't use custom folders at all and only custom labels. This is due to the fact that the ability to have a combined inbox is lost if you use folders. All mail is not sufficient because that includes sent mail and archived mail which isn't the same as a combined inbox. I think it would be beneficial to include the ability to exclude archived mail from other inboxes just like you can with trash and spam. The above labeling issue could also be resolved with having the ability to remove archived or trash/spam mail from a label filter.

I don't want all this, just looking for anyway to keep archive mail in the archive only and trash in the trash only. This includes out of other labels.