Argosoft/php send mail

Hello i have php, apache,mysql and phpnuke on my win32 server we run a argosoft mail server and as you can see it sends mail back and fourth. unfortunatly php isn't sending the mail through it. i though at first it was phpnuke but after running a test from a custom php code written by a friend. and it failing to send an email tells me its the php/argosoft mailserver. so if anyone has any ideas as to how to sort this problem i would love the help i cannot code php and it took us 2 weeks to get the mail server working + dns set up with mx records. thanx for any help in advance Adam White