Hi,
We manage about 6000 mailboxes and I am in direct contact for about a third of them. PST support is an absolute need as many users maintains old archives (due to the quotas put in older Exchange systems). Note that nowadays, most of users stopped creating PST files: workaround would be to import those PST emails in default Archive folder for example. I understand it could be done manually (and we do it that way), but that means 1) to do it before switching to New Outlook (as you lose access to PST files after switching) 2) to take a large amount of time because, as we tested, copying a batch of emails manually from (or to) a PST file is really slow (and risky: if the process stops, it will create duplicates when retrying).
As a feature, I need an email age filter. As far as I know, when online archiving is enabled, users can setup automatic archiving. But without, there is no way to create a "move" automatic action based on email age. Best I found is by date which would mean to change the date on a regular basis.
Finally, if my online email database grows with old emails, I would need a "no index"/"exclude from global search" feature on folders (and sub-folders). Right now I move some emails out of my mailbox (using PST) mainly to keep tidier search results. If everything is to be kept, searching would become a nightmare from Inbox.
Regards,