Subaddressing should be revised. It should be made independent of the feature that allows to specify the folder to send the mail to.
Even if the folder does not exist, it should simply deliver to the Inbox, at least optionally.
Use case: I like to use subaddresses to find out who sold my data. :) So when requesting trial versions, newsletters, etc. I'd like to use a different suffix every time, email@example.com, firstname.lastname@example.org, and when this address gets used by anyone else, I know where it's coming from. And I might be able to block it.
Thank you for sharing your idea to update sub addressing to accept a message even if the folder does not exist. This is already possible by creating an alias for your account such as "email@example.com = firstname.lastname@example.org. By adding this alias you will essentially have an unlimited number of email addresses that will route to your account. This may result in an increase in unwanted email.
Thanks for sharing your idea with us.