Storing messages on a server is useful if you need to read mail from more than one computer. When you log on to your account from a different computer, Outlook Express downloads messages according to the options you have set. You can store messages on a POP3 server. If you have HTTP mail, such as Hotmail, or IMAP mail, your messages are always kept on the server.
Click the Advanced tab, and then select Leave a copy of messages on server.