Two problems I see:
First, using the built-in PHP
mail() function isn’t all that reliable, many would suggest using something like PHPMailer or other more modern library.
Second, you seem to be using the form-fillers email address as the “from” address for sending the email, which won’t work on a lot of mail servers. It is a bad thing to allow mail servers to send from any address, also known as “Open Relay”. Send it from your own email address.
But yes, tell us what error message you get, and on what line.
mail() has been unable to send the email to the mail server, but that’s all you can get from it. Another reason, I believe, that something like PHPMailer is considered better.