I know that this problem has been reported before... 
  in fact many many times before, but I have tried other peoples solutions to it with no success.

I recently recieved this error from the "Phorm" Script, an excelent form processor/result-emailing
script with tons of features:

here is a link to it on my server: 
 http://67.80.121.68:8001/feedback.htm
(this site is just a mock up desgin I made for a me and my friend's joke company btw :)

ERROR
090 - There has been an error, and your information has not been sent.
Alerts:
105 - Mail function failed on user email for template ./feedbackemail.txt.
105P: "sendmail_from" not set in php.ini or custom "From:" header missing
111 - Mail function failed on sending alerts.
111P: "sendmail_from" not set in php.ini or custom "From:" header missing

after reading this is checked my php.ini file for my 'SMTP', and 'sendmail_from' settings:
  they were correct plus the fact that the phorm script provides a from address on its own.

so to amuse myself I simply retyped my SMTP and sendmail_from settings then resaved the file.
I then restarted IIS' services and tried again and recieved the same error.

next, restarted the whole machine tried again and got the same error.

at this point, somewhat annoyed, I made a file doh.php with <?php phpinfo(); ?> being its only contents

browsed to it in my web browser: http://67.80.121.68:8001/sharedocs/doh.php

and it shows that my path for php.ini is correct, but shows:

Directive | Local Value | Master Value
sendmail_from | no value | no value 
SMTP | localhost | localhost

next as a test I added the following lines to doh.php:

ini_set("SMTP","mail-hub.optonline.net");
ini_set("sendmail_from","midimann@optonline.net");
mail("olesoft@hotmail.com","testing","testing");

this worked and I recieved an email... also phpinfo() showed the following:

Directive | Local Value | Master Value
sendmail_from | midimann@optonline.net | no value 
SMTP | mail-hub.optonline.net | localhost 


At this point I have no idea what to do in order to not have to ad ini_set() commands
 to all of my emailing php scripts

any explanations would be extremely appreciated.

PS: i understand that this is a duplicate report and am sorry

also:  i am running ASP, ActivePERL, and PHP under iis. as well as a mysql server.
  could something in that combo be causing this problem?

-best reguards
  Andrew