Our website is developed in PHP and hosted on a Windows Server 2012 running IIS 8. The CMS we use is Website Baker. The site contains a form that should send an email to a specified email address upon a visitor completing it and clicking on submit. Each time we attempted to perform this action, we would get the following error message:
"Could not instantiate mail function".
I finally stumbled across the following link containing a resolution for this issue: http://www.php.net//manual/en/ref.mail.php.
After downloading and unpacking the sendmail.zip and following the directions to modify php.ini and sendmail.ini configuration files, the web form was able to successfully send email messages to the specified email address as well as to the user who submitted it.
Although the above steps resolved our issue, I noticed that the php.ini configuration file contained the wrong SMTP information and we may have been able to resolve the issue just by modifying this file to specify a SMTP Server Host, Port, and Authentication credentials if required.