Configurung Exchange 2000 and PHP mail() function

[LostinIT]

Recently added an Exchange Server to my domain and php doesn't seem to be communicating. (I have verified this through the Exchange logs..it doesn't log anything) I believe it has something to do with my mail settings in my php.ini file as Exchange works in all other respects and all my servers can communicate fine.

Exchange box additions:
1)Set Exchange to allow relays from my webserver box under the virtual SMTP server service.
2)IPSec policy on Exchange box is set to allow all traffic through port 25

The exchange server is on a separate server from my web server. here is what I have tried setting my php.ini file to:
Code:

[mail function]
; For Win32 only.
SMTP = MAIL1 ; for Win32 only
smtp_port = 25
sendmail_from= email@myemail.us ; for Win32 only

; For Win32 only.
;sendmail_from = me@example.com

; For Unix only. You may supply arguments as well (default: "sendmail -t -i").
;sendmail_path =


I have also tried entering the macines direct I.P. address:
Code:

[mail function]
; For Win32 only.
SMTP = 192.168.254.xxx ; for Win32 only
smtp_port = 25
sendmail_from= email@myemail.us ; for Win32 only

; For Win32 only.
;sendmail_from = me@example.com

; For Unix only. You may supply arguments as well (default: "sendmail -t -i").
;sendmail_path =


Anyone know of any good resources or have had experience with this issue? Are there any other parameters in my php.ini I need to set?

Environment:

W2k Server
Exchange 2k Server

Grateful for any help...