Can receive email, but can't have the server send email

I have a script that is supposed to have the server send an email. My problem is, that I can email my server, and receive that email, but the server will not send email. Will only send email through the squirrelmail interface. I have the MX record as: mail.mydomain.com and mydomain.com and an A record of mail.mydomain.com

Below is the script that should have the server send an email.

<?php
$fileatt = "Reports/$previousreport/$previousreport.pdf"; // Path to the file 
$fileatt_type = "application/pdf"; // File Type 
$fileatt_name = "$previousreport"; // Filename that will be used for the file as the attachment 

$email_from = "example.com"; // Who the email is from
$email_cc开发者_运维问答 = "example@example.com"; 
$email_subject = "$theData3"; // The Subject of the email 
$email_message = "<br>";
$email_message .= "<br>"; // Message that the email has in it 

$email_to = "$theData2"; // Who the email is to 

$headers = "From: ".$email_from. 
$headers = "\r\nCc: ".$email_cc;


$file = fopen($fileatt,'rb'); 
$data = fread($file,filesize($fileatt)); 
fclose($file); 

$semi_rand = md5(time()); 
$mime_boundary = "==Multipart_Boundary_x{$semi_rand}x"; 

$headers .= "\nMIME-Version: 1.0\n" . 
"Content-Type: multipart/mixed;\n" . 
" boundary=\"{$mime_boundary}\""; 

$email_message .= "This is a multi-part message in MIME format.\n\n" . 
"--{$mime_boundary}\n" . 
"Content-Type:text/html; charset=\"iso-8859-1\"\n" . 
"Content-Transfer-Encoding: 7bit\n\n" . 
$email_message .= "\n\n"; 

$data = chunk_split(base64_encode($data)); 

$email_message .= "--{$mime_boundary}\n" . 
"Content-Type: {$fileatt_type};\n" . 
" name=\"{$fileatt_name}\"\n" . 
//"Content-Disposition: attachment;\n" . 
//" filename=\"{$fileatt_name}\"\n" . 
"Content-Transfer-Encoding: base64\n\n" . 
$data .= "\n\n" . 
"--{$mime_boundary}--\n"; 

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

if($ok) { 
echo "<font face=verdana size=2><center>You file has been sent<br> to the email address you specified.<br> 
Make sure to check your junk mail!";

} else { 
die("Sorry but the email could not be sent. Please go back and try again!"); 
} 
?>

I keep checking the MX records but I can't figure out what is wrong.

Check the log files for any hints (/var/log/messages or /var/log/maillog).

Could you also better format your code to help me understand what exactly you are trying to achieve.

I doubt the issue is with the MX, more likely it's a coding problem (the $email_from variable has an incorrectly formatted address)