Yeah, that's my impression as well. I've been wondering about this sort of setup for a while – there's a lot of moving parts in traditional email servers, and projects like poste or univention/zimbra/… that just try to glue these massive stacks together have always been far too fragile and involved for any setup that's smaller than "we can afford a dedicated sysadmin for emailling".
The only feature I'd still want is Sieve, then it'd be good enough for not just home setups, but probably also SMBs.
It doesn't look like it supports mailbox sharing or public folders, which are very helpful for collaborating in a SMB, especially with shared email addresses (e.g., sales@business.com).
Do you know how this is typically used/configured? Do accounts get this shared account (mailbox(es)/folders with messages) as folders in their own account? So next to your own Inbox and Trash, you would have Sales/Inbox and Sales/Trash? If you delete a message from Sales/Inbox, does it automatically go to Sales/Trash? How is that done? Perhaps IMAP namespaces?
I have figured folks can just add another account (IMAP connection) to their mail client. Either a shared account (e.g. sales@), or account of a colleague. And then the account (mailbox) is shared.
Perhaps it's because webmails are just for a single account and folks would have to have multiple mail browser windows open? Or business folks are just not used to this approach? Or perhaps they want an admin to inject some shared mailbox into an existing account without requiring any user action?
Public folders sound a bit like a mailing list, from what I just skimmed from Exchange documentation. I presume the message flags (Seen/Read) are per-user? So it's more like delivery to each members copy of the public folder, instead of an actual shared folder?
I use dovecot and there is a lot of configurability for shared and public folders.
Public folders are much nicer than having to add separate IMAP accounts; users can subscribe to whatever public folders they want/need from a list. All subscribed folders show up underneath the root namespace folder. I have about 6 types of inboxes based on business roles (sales, pr, hr, it, etc). I have many more folders, beyond general inboxes, that get filled based on sieve filter rules. For example, voicemail alerts get filtered into a special voicemail folder.
Dovecot lets you configure whether the read state is shared or per user.
We use a system where people can flag messages as to whether they are taken for action, are critical, or are completed. These show up in Thunderbird/Roundcube mailbox list as color coded, and this aids in people knowing if emails have been dealt with.
You still have strict control for access/permissions on a per-mailbox basis, with ACL.
All of this could have been done with shared folders under a "shared" user account (either one or multiple shared account, such as sales, hr, etc) with similar results.
The only feature I'd still want is Sieve, then it'd be good enough for not just home setups, but probably also SMBs.