what E-Mail provider do you use and why
what E-Mail provider do you use and why
Sadly, yes. A Proton team member on Reddit confirmed it a couple years back:
Folder/label names are visible to the server (for filters and other reasons) as are email metadata. Message and attachment contents are encrypted and not visible to the server.
old.reddit.com/r/ProtonMail/comments/…/fzc6wry/
Do note that this is ONLY true for Mail. Calendar, and Drive does encrypt folders/label names.