I had a question that I couldn't find an answer to. We use o365 for email and Outlook 2013 although I had this problem before we went to o365. I have cleanup rules setup on each folder for retention. Example: Inbox items get deleted after 36 months, deleted items after 12 months, other folders range from 3-6 months.
I noticed my rules don't work on some folders with longer retention and then realized that it only deletes the emails that are in the OST. So if my OST keeps 3 months of inbox emails, it will never delete the older ones (the ones past where it says there are more items to view on the server, click here to view more on Microsoft Exchange). The folders that have one month of retention delete just fine.
The OST size is set by policy.
Is there a way to have a rule see the online email as well as the offline email?