Selecting older messages takes over 1 second each
When a folder has many items (in my case 250+), selecting those at the bottom of the folder takes over 1 second each. By comparison, selecting items at the top of the folder is nearly instant.
1. Open a folder with a couple hundred messages
2. Select (check box) two or three at the top and observe the time it takes for the check mark to appear (nearly instant).
3. scroll to the bottom of the list.
4. Check two or three items and observe the time it takes for the checkbox to appear (over 1 second).