sending file attachments and some questions about proxy

[ITlover]

I have a Microsoft Exchange Server 2003 and I I try to access e-mails in my WinXP Computer through microsoft outlook. I have my WinXP Computer and the Microsoft Exchange Server
both in my local area network. Now my question is that when I send an e-mail with a file attached to it from my one WinXP Computer to another user who also has a mail box in same Exchange Server, does it uses FTP protocol ?

I hope my question is clear,