php 5 mail() function failure

[jamesk]

i searched these boards without finding anyone else having had this problem... so, i will post and hope that somebody knows what might be going on.

i am running vb 3.6.8 patch level 1 on Windows 2003 Server IIS with php 5 in isapi mode. the php mail() function fails to send mail without logging any error or reporting (http 500) any error in the forums webpages (register.php for example).

i am able to send mail if i switch to an smtp server in the email settings for the forum. however, i want to solve the issue for several reasons but primarily becasue of "relay" problems.

maybe i am missing something obvious but i have successfully run vb on various environments since v1 and now i have a "mental block" trying to solve this one.

thanks for any help you may be able to provide.