There is a problem deleting thousands of emails from the Live Mail server. This appears to occur when the user is accessing emails via the web mail version (outlook.com) and not deleting emails at all.
My experience when using Live Mail only on the local computer (not web mail) that when permanently deleting emails that they are removed from the server.
However I have client who has used the web mail for years and accumulated 7000 Sent and 5000+ within the Inbox. Upon installing Live Mail on their computer a massive download occurs. The client was then asked to clean up the emails in the local Live Mail believing that synch would remove from the server.
Twice now I have had to installed Live mail and each time the masses of emails are downloaded, apparently the local deletes did not synch. So I have permanently fixed the problem by logging into the web mail version and permanently deleting the masses. I found deleting the Inbox a pain in that when the oldest emails are displayed that only 35 can be deleted at a time. A work around is to delete all Inbox emails then open Deleted items and select the number of most recent emails required and move them back to the Inbox.
I believe that there should be an added function that enables the user to choose that all emails in the Inbox be deleted after a number of daysdefined by the user.