Hi,
"Will all the items (including the ones not deleted) older than X days be deleted or just the ones my users deleted?"
No, only the files in the dumpster will be affected by the the attributes: zimbraDumpsterEnabled ; zimbraDumpsterPurgeEnabled ; zimbraDumpsterUserVisibleAge ; zimbraMailDumpsterLifetime
You may also tweak this as admin, in the adminUI.
"Also, does it work for my version?"
I did not tried this in your version, but my guess is "yes". If you want to make sure, just use the adminUI to do it.
Also, and as a warning to have caution, although these 4 attributes won't affect mails that are not under the "dumpster" folder, there are others that do indeed, will delete items under any other folder. Be carefull when you change these things. I've seen some little "disasters" because of one admin confusing the attribute/configuration.
Just in case you want to be really really really sure
, you could just modify 1 test user, and after you confirm the behaviour is what you expect, apply that to the rest of users (via cos).
gl!