ChinaLamb wrote:

Is it possible to have two different clients to have two different
subscriptions to the folders, or should all clients have the same
subscription?

While I would expect each client to be able to have its own subscription
setting, I've seen postings that state that changing the subscription list
on one client changes it on another. I haven't checked that myself, but I
don't doubt the observations posted by others.

Is there a specific imap specification for this somewhere?

Subscriptions for IMAP folders aren't well-explained anywhere that I've
seen. My own sense is that by subscribing to a folder, you tell Outlook to
synchronize those folders during each send/receive and download their
contents to the local cache. You can use your subscriptions to control
which folders are visible in the Outlook folder list.
--
Brian Tillman [MVP-Outlook]