How can I get Outlook to change faster between email previews?

[Guest]

When I open Outlook, it sometimes works at a normal speed and sometimes it
takes thirty seconds (sometimes more sometimes less) to switch from one email
in the preview pane to the next. This has been going on for weeks. Any idea
what's causing this?

 

[Guest]

I've been having the same problem for the last 3-5 weeks. Can't find a
solution.