Email is accessed and exchanged and sync'ed between a server and a client.
POP, IMAP (incoming information to client) and SMTP (outgoing information to server) and HTTP (outgoing and incoming) are protocols used to exchange this information.
The penny has dropped that you need to use the IMAP protocol and not POP to use folders and keep those at the client in sync with the server.
To allow these 2 employees IMAP email access from anywhere, anytime - a) Just tell them to use their smartphone, which will likely have an IMAP-capable client b) You can install a web-based IMAP-capable client on your website, such as Roundcube, they can then simply go to website.com/email and log in with the username and password. Often the hosting company will have an automatic ability in their control panel to do all this for you with just a few clicks.