transfering email to another pc

hello,
I know this is possible, I just can’t remember how to do it. We just got new laptops at my company and I need to transfer everyone emails from their POP3 accounts from their current desktops to the laptops. We are no longer going to use the desktops at all. Some use Outlook and some use Outlook Express. This way, anything that is in their current inbox or saved in folders will be available on the laptops. Thanks for any suggestions.