How to detect TRUE value from mail function?

[toplisek]

an example:

 if (mail($to, $subject, $message, $headers)) {
    // Display CONTAINER
   $CONTAINER = ' <div</div>';
  }

How to detect TRUE value from such function?
Just as an example:

$response = array(
  'success_container' => true,
 );

and if TRUE it will be pushed container (just as an example to show intent):

<?php

if ( is_success_container()) {
echo($CONTAINER);
}
?>