PHP Mail form not sending emails on Linux server - php

Question

This is my code and my form... it acts like the email was sent, but it never arrives.
I would like to know what could possibly be wrong... Anyone?
The website is hosted on a Linux server, and I don't really know if the server could be blocking the emails because of some kind of incompatibility... I don't really know what it could be.
<?php
if($_POST)
{
//check if its an ajax request, exit if not
if(!isset($_SERVER['HTTP_X_REQUESTED_WITH']) AND strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) != 'xmlhttprequest') {
die();
}
$to_Email = "myemail#gmail.com"; //Replace with recipient email address
$subject = 'Ah!! My email from Somebody out there...'; //Subject line for emails
//check $_POST vars are set, exit if any missing
if(!isset($_POST["userName"]) || !isset($_POST["userEmail"]) || !isset($_POST["userPhone"]) || !isset($_POST["userMessage"]))
{
die();
}
//Sanitize input data using PHP filter_var().
$user_Name = filter_var($_POST["userName"], FILTER_SANITIZE_STRING);
$user_Email = filter_var($_POST["userEmail"], FILTER_SANITIZE_EMAIL);
$user_Phone = filter_var($_POST["userPhone"], FILTER_SANITIZE_STRING);
$user_Message = filter_var($_POST["userMessage"], FILTER_SANITIZE_STRING);
//additional php validation
if(strlen($user_Name)<4) // If length is less than 4 it will throw an HTTP error.
{
header('HTTP/1.1 500 Name is too short or empty!');
exit();
}
if(!filter_var($user_Email, FILTER_VALIDATE_EMAIL)) //email validation
{
header('HTTP/1.1 500 Please enter a valid email!');
exit();
}
if(!is_numeric($user_Phone)) //check entered data is numbers
{
header('HTTP/1.1 500 Only numbers allowed in phone field');
exit();
}
if(strlen($user_Message)<5) //check emtpy message
{
header('HTTP/1.1 500 Too short message! Please enter something.');
exit();
}
//proceed with PHP email.
$headers = 'From: '.$user_Email.'' . "rn" .
'Reply-To: '.$user_Email.'' . "rn" .
'X-Mailer: PHP/' . phpversion();
#$sentMail = mail($to_Email, $subject, $user_Message .' -'.$user_Name, $headers);
if(!$sentMail)
{
header('HTTP/1.1 500 Couldnot send mail! Sorry..');
exit();
}else{
echo 'Hi '.$user_Name .', Thank you for your email! ';
echo 'Your email has already arrived in my Inbox, all I need to do is Check it.';
}
}
?>
Here's my form:
<fieldset id="contact_form">
<legend>My Contact Form</legend>
<div id="result"></div>
<input type="text" name="name" id="inputt" placeholder="Enter Your Name" />
<input type="text" name="email" id="inputt" placeholder="Enter Your Email" />
<input type="text" name="phone" id="inputt" placeholder="Phone Number" />
<textarea name="message" id="message" placeholder="Enter Your Name"></textarea>
<button class="submit_btn" id="submit_btn">Submit</button>
</fieldset>

Answer 1

Your $headers are wrong, you're appending "rn" instead of "\r\n". Try this instead:
$headers = 'From: '.$user_Email. "\r\n" .
'Reply-To: '.$user_Email. "\r\n" .
'X-Mailer: PHP/' . phpversion();

Answer 2

According from your comment out of the maillog you need to adjust your php.ini to include the --r argument to your sendmail_path.
By default it usually is:
sendmail_path = /usr/sbin/sendmail -t -i
Apparently you are using another argument that also requires the --r argument. Appending that to your sendmail_path should get a long way.