Problem with PHP, SendMail and IIS?

Hello, I will really appreciate everybody's input on this.

I have a server running Windows Server 2012 R2 with IIS 8.5.96 and PHP 5.6.

I have a PHP website running on this server, for which I setup SendMail to send e-mails like password resets, etc. Initially, my setup worked properly, I could send e-mails using a mailtest.php page and other PHP files; however, it just stopped working all of a sudden. One thing I noticed was that, when I tried to run the mailtest.php page, the web browsers just hang there waiting to load until they eventually give up (below), but every other PHP page works, including PHPInfo. This makes me believe the problem lies somewhere in PHP or FastCGI, but I can't seem to find a way to confirm that.

HTTP Error 500.0 - Internal Server Error

C:\Program Files (x86)\PHP\v5.6\php-cgi.exe - The FastCGI process exceeded configured request timeout

DetailedErrorInformation:ModuleFastCgiModuleNotificationExecuteRequestHandlerHandler    PHP_via_FastCGI ErrorCode0x80070102Requested URL    http://mysite.com:80/mailtest.php PhysicalPath    C:\inetpub\sites\mysite.com\mailtest.php LogonMethodAnonymousLogonUserAnonymous

Any ideas?

Are there any logs I can look at? The SendMail log shows nothing.

When should I start looking?

I included my SendMail.ini and PHP.ini config below. Again, this was working and then it wasn't; but I didn't make any changes.

My SendMail.ini

[sendmail]

smtp_server=smtprelay.mailserver.com; smtp port (normally 25)
smtp_port=25

My PHP.ini

[mail function];ForWin32 only.; http://php.net/smtp
SMTP = localhost; http://php.net/smtp-port
smtp_port =25;ForWin32 only.; http://php.net/sendmail-from
sendmail_from = support@mysite.com;ForUnix only.You may supply arguments as well (default:"sendmail -t -i").; http://php.net/sendmail-path
sendmail_path ="C:\usr\lib\sendmail.exe -t"

 Thanks in advance for any input on this.