The email address above looks like your assigned default webhost email, and is likely used due to not assigning your own value for the "From" value in your email form.
Although you can assign your desired "FROM" value to "JohnLee@webhost.com" I would not suggest this unless you actually own said email adddress.
Yes, you may define the "From" values in your mail script.
//DEFINE SOME VARIABLES
$to = "$_POST[email];
$subject = "Your email subject line";
$message = "$_POST[message]";
$adminemail = "email@example.com"
$website = "www.yourdomain.com";
// SEND THE EMAIL AS PER DEFINED VARIABLES
mail($to, $subject, $message, "From: $website <$adminemail>\n");