Suggestion: allow configuring an auto-delete after X days and auto-archival after X days per folder

I want to suggest to allow configuring an auto-delete after X days and auto-archival after X days per folder. A good use case are high frequency mailing lists, where for storage reasons alone it may not make much sense to store them for longer than 4-6 weeks. Another one might be monitoring mails.

There currently seems to be a per-folder auto-archival after a fixed 90 days, but 1. this doesn't seem to allow instantly permanently deleting the e-mail to free the storage, and 2. it doesn't allow entering a custom amount of days.

Thunderbird and other mail clients already have this feature, but many mobile clients don't, also some people use the web UI exclusively.