echo "Test mail from postfix" | mail -s "Test Postfix" admin@something.com

php -a mail ('admin@something.com', "Test Postfix", "Test mail from postfix"); exit ();

Return-Path: <bounced@yourdomain.com>

@mail($email_to, $email_subject, $email_message, $headers);

error_reporting(E_ALL) ;
ini_set('display_errors', 1) ;

<?php

error_reporting(E_ALL) ;
ini_set('display_errors', 1) ;

if(isset($_POST['email'])) {
     
    // EDIT THE 2 LINES BELOW AS REQUIRED
    $email_to = "testmail123@primasmedia.co.uk";
    $email_subject = "Villacalmia.co.uk contact enquiry";
     
     
    function died($error) {
        // your error code can go here
        echo "We are very sorry, but there were error(s) found with the form you submitted. ";
        echo "These errors appear below.<br /><br />";
        echo $error."<br /><br />";
        echo "Please go back and fix these errors.<br /><br />";
        die();
    }
     
    // validation expected data exists
    if(!isset($_POST['first_name']) ||
        !isset($_POST['last_name']) ||
        !isset($_POST['email']) ||
        !isset($_POST['telephone']) ||
        !isset($_POST['comments'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');       
    }
     
    $first_name = $_POST['first_name']; // required
    $last_name = $_POST['last_name']; // required
    $email_from = $_POST['email']; // required
    $telephone = $_POST['telephone']; // not required
    $comments = $_POST['comments']; // required
     
    $error_message = "";
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
  if(!preg_match($email_exp,$email_from)) {
    $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
  }
    $string_exp = "/^[A-Za-z .'-]+$/";
  if(!preg_match($string_exp,$first_name)) {
    $error_message .= 'The First Name you entered does not appear to be valid.<br />';
  }
  if(!preg_match($string_exp,$last_name)) {
    $error_message .= 'The Last Name you entered does not appear to be valid.<br />';
  }
  if(strlen($comments) < 2) {
    $error_message .= 'The Comments you entered do not appear to be valid.<br />';
  }
  if(strlen($error_message) > 0) {
    died($error_message);
  }
    $email_message = "Form details below.\n\n";
     
    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }
     
    $email_message .= "First Name: ".clean_string($first_name)."\n";
    $email_message .= "Last Name: ".clean_string($last_name)."\n";
    $email_message .= "Email: ".clean_string($email_from)."\n";
    $email_message .= "Telephone: ".clean_string($telephone)."\n";
    $email_message .= "Comments: ".clean_string($comments)."\n";
     
     
// create email headers
$headers = 'From: '.$email_from."\r\n".
'Reply-To: '.$email_from."\r\n" .
'Return-Path: <bounced@primasmedia.co.uk>'.
'X-Mailer: PHP/' . phpversion();
mail($email_to, $email_subject, $email_message, $headers);  
?>
 
<!-- include your own success html here -->
 
Thank you for contacting us. We will be in touch with you very soon.
 
<?php
}
?>

$success = mail($email_to, $email_subject, $email_message, $headers);
echo 'The email ' . (($success) ? 'worked!' : 'failed.') . '<br />';

The email worked!
Thank you for contacting us. We will be in touch with you very soon.

Fatal error: Call to undefined function sendmail() in /var/www/villacalmia.co.uk/send_form_email.php on line 74

sendmail_path = /usr/local/bin/phpsendmail

sendmail_path = /usr/local/bin/phpsendmail

<?php
phpinfo();

sendmail_path = /usr/local/bin/phpsendmail

<?php
phpinfo();

The email worked!
Thank you for contacting us. We will be in touch with you very soon.