Email Validation not working... Always sends never wrong! help?

programming
1

I just want one field to validate the email, currently it is sending no matter what is entered in to the form field…? What is wrong with my code your help is much appreciated.
Thanks.


<?php

function checkEmail($txtEmail)
{
  if(!eregi("^[a-zA-Z0-9_]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$", $txtEmail))
  {
     return FALSE;
  }

  list($Username, $Domain) = split("@",$txtEmail);

  if(getmxrr($Domain, $MXHost))
  {
     return TRUE;
  }
  else
  {
     if(fsockopen($Domain, 25, $errno, $errstr, 30))
     {
        return TRUE;
     }
     else
     {
        return FALSE;
     }
  }
}

$sendTo = "me@mydomain.co.uk";
$subject = 'Add Me To The Mailing List';

$headers = "From: " . $_POST["txtEmail"];

$message = 'Hey,'."

". $_POST["txtEmail"] . ' would like to join the mailing list.';
  
$success = mail($sendTo, $subject, $message, $headers);
if ($success){
header("location: http://www.mydomain.co.uk/thanks.html");
} else {
echo "Sorry there was an error, please go back and try again!";
}

if(checkEmail ($txtEmail) == FALSE)
{
echo "sorry that email address does not exist! Please go back and try again";
} 
else{
header("location: http://www.mydomain.co.uk/error.html");
}


?>