How to use Mail.php class for custom contact form

[n13design]

I have a form that customers use to create a service request.  The information they put in the form is added to a database.  A confirmation email is sent to the customer and to us, the admin, using the php mail() function located in the controller file.  The problem admin doesn't receive the email.  It doesn't show up in spam.  We confirmed the function works be sending the email to @gmail.com rather than @ourdomain.com.  We tried using Mandrill in Advanced Parameters.  It still wont send directly to @ourdomain.com.

 

Emails sent from the contact form work fine. 

 

I'm not sure which direction to take the fix for this.  Should I use the mail.php class to send the email?  Should I edit the DNS for the server and add an MX.  Should I use a different SMTP in the Advance Parameters.