correct use of add_settings_error in wordpress

<?php
// Register your settings (this goes in your plugin file or
// if registering theme options, in your functions.php file
function register_my_plugin_options()
{

register_setting( 'my_plugin_options', 'my_plugin_options', 'my_plugin_validation_cb' );
add_settings_section( 'my_plugin_main', 'Main Plugin Options', 'my_plugin_main_settings', 'my_plugin_slug' );
add_settings_field( 'send-email-to', 'Send email notices to:', 'my_plugin_main_email_input', 'my_plugin_main', 'my_plugin_slug' );

}
add_action( 'admin_init', 'register_my_plugin_options' );

function my_plugin_main_settings()
{
  // do stuff here
}

function my_plugin_main_email_input()
{
  // you would output your form field here
}

// Function for validating all your various settings
function my_plugin_validation_cb( $input )
{
  $valid = array();
  $options = get_option( 'my_plugin_options' );

  if( $input['send-email-to'] != sanitize_email( $input['send-email-to'] ) )
  {
    add_settings_error(
      'send-email-to',
      'send-email-field-error',
      "You supplied an invalid email address!",
      'error'
    );
  } else {
    $valid['send-email-to'] = $input['send-email-to'];
  }

  return $valid;
}

// Example function that would render your options page content
function render_my_plugin_options_page()
{
?>
<div class="wrap">
  <h2>My Plugin Options</h2>

<?php // IMPORTANT!!! If you want your settings fields to display errors,
      // Call settings errors here!
      settings_errors(); ?>

  <?php
  // echo out the form and other settings info here

}