We are in the process of moving mailboxes from our old Exchange 2003 server to a new Exchange 2010 server. One thing that we just noticed is that for mailboxes that are moved to Exchange 2010, the Junk email filtering no longer works in Outlook 2007 or Outlook 2010, when it used to work fine when the mailboxes were on Exchange 2003. The settings look correct in Outlook, and filtering is definitely enabled (users are retaining all of their settings in Outlook anyway). All users are connecting to Exchange directly from Outlook, no POP3 or IMAP, etc. I've checked 3-4 clients and so far every one of them has this problem.
I've tried creating a new Outlook profile, still the same issue. I tried the "rules upgrade" in Outlook 2010 which did not help. I've added a known external email address in the Blocked Senders list, and it comes through to the Inbox every time.
Has anybody seen this issue or know of any workaround for it? We've been trying various things and so far nothing is working.