Got same email three times with POP3 account in Exchange 2003 Server

I am setting up Exchange 2003 server and did some test in Outlook. One user have 3 different email accounts, he is one of users in AD, have one mailbox in Exchange server. I enabled Default POP3 Virtual Server, setup 3 email account with POP3, no Exchange Server account. When I sent test email by using my email account to one of email address of this user, this user got the same email three times. Is anybody know what’s wrong? How to solve this problem? Thank you very much!