A while back I noticed that every time I do a send/receive email in Outlook the final step of synchronizing subscribed folders is very slow, often taking minutes. I even hear for some people the process hangs. Searching the Google forums turned up a solution by 7amb that worked for me. Here’s a paint-by-numbers version of the answer.
Step 3. Scroll Down to the Send and receive section.
Step 4. Click the Send/Receive… button.
Step 7. Uncheck the Get folder unread count for subscribed folders
Step 8. Select the Use the custom behavior defined below radio button
Step 9. Make sure only the Inbox is checked.
Click OK and exit out of the options and do a send/receive to verify the problem is solved. It worked for me.