The shared folder support in Fastmail is one of my favorite features. Of course you can achieve similar outcomes in MS365 (not difficult) or Google Workspace*,

The shared folder support in Fastmail is one of my favorite features. Of course you can achieve similar outcomes in MS365 (not difficult) or Google Workspace*, but it’s much more straightforward in Fastmail than in any other email service I’ve used or administered. * As of a few years ago this was annoying with Workspace (then G Suite), having to hop between delegated Gmail inboxes via the web UI.