wpmail_exceptions.php

<?php
defined( 'ABSPATH' ) OR exit;
/**
 * Plugin Name: (WCM) PHPMailer Exceptions & SMTP
 * Description: WordPress by default returns <code>FALSE</code> instead of an <code>Exception</code>. This plugin fixes that.
 */

add_action( 'phpmailer_init', 'WCMphpmailerException' );
function WCMphpmailerException( $phpmailer )
{
  if ( ! defined( 'WP_DEBUG' ) OR ! WP_DEBUG )
	{
		$phpmailer->SMTPDebug = 0;
		$phpmailer->debug = 0;
		return;
	}
	if ( ! current_user_can( 'manage_options' ) )
		return;

	$phpmailer->SMTPDebug = 2;
	$phpmailer->debug     = 1;

	$data = apply_filters(
		'wp_mail',
		compact( 'to', 'subject', 'message', 'headers', 'attachments' )
	);

	current_user_can( 'manage_options' )
		AND print htmlspecialchars( var_export( $phpmailer, true ) );

	$error = null;
	
	try
	{
		$sent = $phpmailer->Send();
		! $sent AND $error = new WP_Error( 'phpmailerError', $sent->ErrorInfo );
	}
	catch ( phpmailerException $e )
	{
		$error = new WP_Error( 'phpmailerException', $e->errorMessage() );
	}
	catch ( Exception $e )
	{
		$error = new WP_Error( 'defaultException', $e->getMessage() );
	}

	if ( is_wp_error( $error ) )
		return printf(
			"%s: %s",
			$error->get_error_code(),
			$error->get_error_message()
		);
}