CC Proxy can work as mail proxy server for Office Outlook.

CCProxy is an easy-to-use proxy server software. Full supports Windows 98/ME/NT/2000/XP. For more details of CCProxy, please click here. Also you can download it here for a trial.

Suppose your mail account information is -

login user name(account):aaa
login password:bbb
pop3 server address(incoming server address):ccc
smtp server address(outcoming server address):ddd
smtp login user name:eee (sometimes same as pop3 login user name)
smtp login password:fff (sometimes same as pop3 login password)

Suppose your proxy address is 192.168.0.1

You need to change your mail account information in your Outlook as:

login user name(account):aaa#ccc
login password:bbb
pop3 server address(incoming server address):192.168.0.1
smtp server address(outcoming server address):192.168.0.1
smtp login user name:eee#ddd
smtp login password:fff

Notes: if you are using office 2002 or office XP, you need install office sp1 first.