How to deliver same mail to 4 different accounts

I have a customer who is currently using very old POP3 client software (Eudora) for e-mail. For the purpose of this ticket let's call him "joe@example.com". Joe called me today and said that he wanted to begin testing 3 new POP3 email clients - ultimately choosing one to replace Eudora. - Outlook (Mac) - Apple Mail - MailPile What he wants to have happen is that when incoming mail to "joe@example.com" is received at the server, is that he wants a COPY of the incoming message forwarded/copied to 3 new different real email accounts (ie. they have passwords to login) outlook@example.com applemail@example.com mailpile@example.com while at the same time having the original incoming message delivered to his current account "joe@example.com". In this way he can test each client application to see which one he prefers to use ..... In other words, each incoming message gets delivered to all 4 accounts automatically. In this way his current email client (Eudora) continues to receive all his mail uninterrupted, but the client software he wants to test to see which one he likes best all get copies of the same incoming messages. I can't figure out a way to do this. Forwarders allow an alias to forward to a real address, but I don't know how to make a real address COPY to 3 other real addresses. Any suggestions are appreciated. Thanks