编辑文件

编辑文件：MailCatcherTrait.php

<?php

namespace WPMailSMTP;

use Exception;
use WPMailSMTP\Admin\DebugEvents\DebugEvents;
use WPMailSMTP\Providers\MailerAbstract;

/**
 * Trait MailCatcherTrait.
 *
 * @since 3.7.0
 */
trait MailCatcherTrait {

/**
	 * Debug output buffer.
	 *
	 * @since 3.3.0
	 *
	 * @var array
	 */
	private $debug_output_buffer = [];

/**
	 * Debug event ID.
	 *
	 * @since 3.5.0
	 *
	 * @var int
	 */
	private $debug_event_id = false;

/**
	 * Whether the current email is a test email.
	 *
	 * @since 3.5.0
	 *
	 * @var bool
	 */
	private $is_test_email = false;

/**
	 * Whether the current email is a Setup Wizard test email.
	 *
	 * @since 3.5.0
	 *
	 * @var bool
	 */
	private $is_setup_wizard_test_email = false;

/**
	 * Whether the current email is blocked to be sent.
	 *
	 * @since 3.8.0
	 *
	 * @var bool
	 */
	private $is_emailing_blocked = false;

/**
	 * Holds the most recent error message.
	 *
	 * @since 3.7.0
	 *
	 * @var string
	 */
	protected $latest_error = '';

/**
	 * Last error code captured before PHPMailer clears it.
	 *
	 * Populated via setError() override with first-write-wins semantics.
	 *
	 * @since 4.8.0
	 *
	 * @var string
	 */
	private $last_error_code = '';

/**
	 * Email addresses PHPMailer reported as failed during postSend().
	 *
	 * PHPMailer dispatches doCallback() per recipient in smtpSend(), and per recipient
	 * under SingleTo=true in mailSend()/sendmailSend().
	 *
	 * @since 4.9.0
	 *
	 * @var string[]
	 */
	private $failed_recipients = [];

/**
	 * Modify the default send() behaviour.
	 * For those mailers, that relies on PHPMailer class - call it directly.
	 * For others - init the correct provider and process it.
	 *
	 * @since 1.0.0
	 * @since 1.4.0 Process "Do Not Send" option, but always allow test email.
	 * @since 4.5.0 Add support for logging blocked emails.
	 *
	 * @throws Exception When sending via PhpMailer fails for some reason.
	 *
	 * @return bool
	 */
	public function send() { // phpcs:ignore Generic.Metrics.CyclomaticComplexity.TooHigh

// Reset email related variables.
		$this->debug_event_id             = false;
		$this->is_test_email              = false;
		$this->is_setup_wizard_test_email = false;
		$this->is_emailing_blocked        = false;
		$this->latest_error               = '';
		$this->failed_recipients          = [];

if ( wp_mail_smtp()->is_blocked() ) {
			$this->is_emailing_blocked = true;
		}

// Always allow a test email - check for the specific header.
		foreach ( (array) $this->getCustomHeaders() as $header ) {
			if (
				! empty( $header[0] ) &&
				! empty( $header[1] ) &&
				$header[0] === 'X-Mailer-Type'
			) {
				if ( trim( $header[1] ) === 'WPMailSMTP/Admin/Test' ) {
					$this->is_emailing_blocked = false;
					$this->is_test_email       = true;
				} elseif ( trim( $header[1] ) === 'WPMailSMTP/Admin/SetupWizard/Test' ) {
					$this->is_setup_wizard_test_email = true;
				}
			}
		}

// Log blocked emails if the option is enabled.
		if ( $this->is_emailing_blocked ) {
			/**
			 * Fires when an email is blocked from being sent.
			 *
			 * @since 4.5.0
			 *
			 * @param MailCatcherInterface $mailcatcher The MailCatcher object.
			 */
			do_action( 'wp_mail_smtp_mail_catcher_send_blocked', $this );

return false;
		}

// If it's not a test email,
		// check if the email should be enqueued
		// instead of being sent immediately.
		if ( ! $this->is_test_email && ! $this->is_setup_wizard_test_email ) {

/**
			 * Filters whether an email should be enqueued or sent immediately.
			 *
			 * @since 4.0.0
			 *
			 * @param bool  $should_enqueue Whether to enqueue an email, or send it.
			 * @param array $wp_mail_args   Original arguments of the `wp_mail` call.
			 */
			$should_enqueue_email = apply_filters(
				'wp_mail_smtp_mail_catcher_send_enqueue_email',
				false,
				wp_mail_smtp()->get_processor()->get_filtered_wp_mail_args()
			);

$queue = wp_mail_smtp()->get_queue();

// If we should enqueue the email,
			// and the email has been enqueued,
			// bail.
			if ( $should_enqueue_email && $queue->enqueue_email() ) {
				return true;
			}
		}

$connection  = wp_mail_smtp()->get_connections_manager()->get_mail_connection();
		$mailer_slug = $connection->get_mailer_slug();

// Define a custom header, that will be used to identify the plugin and the mailer.
		// phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
		$this->XMailer = 'WPMailSMTP/Mailer/' . $mailer_slug . ' ' . WPMS_PLUGIN_VER;

// Clear any prior failure entry for this connection. The smtp_send()/api_send()
		// catch paths set a fresh entry on failure; on success no further action needed.
		EmailSendingDebug::clear( $connection->get_id() );

// Use the default PHPMailer, as we inject our settings there for certain providers.
		if (
			$mailer_slug === 'mail' ||
			$mailer_slug === 'smtp' ||
			$mailer_slug === 'pepipost'
		) {
			return $this->smtp_send( $connection );
		} else {
			return $this->api_send( $connection );
		}
	}

/**
	 * Send email via SMTP.
	 *
	 * @since 4.0.0
	 *
	 * @param ConnectionInterface $connection The connection object.
	 *
	 * @throws Exception When sending via PhpMailer fails for some reason.
	 *
	 * @return bool
	 */
	private function smtp_send( $connection ) { // phpcs:ignore Generic.Metrics.CyclomaticComplexity.TooHigh

// Reset captured SMTP error code from previous send attempts.
		$this->last_error_code = '';

$mailer_slug = $connection->get_mailer_slug();

// phpcs:disable WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
		try {
			// Capture PHPMailer's SMTPDebug output whenever the admin has DebugEvents
			// enabled, or whenever the current send is an admin test email - test sends
			// always want diagnostics regardless of the global debug setting.
			if ( DebugEvents::is_debug_enabled() || $this->is_test_email ) {
				$this->Debugoutput = [ $this, 'debug_output_callback' ];

if ( $this->is_test_email ) {
					/**
					 * Filters the PHPMailer SMTPDebug verbosity for admin test emails.
					 *
					 * Levels: 0 (off), 1 (client commands), 2 (commands + server responses),
					 * 3 (commands + data + connection status), 4 (low-level data).
					 *
					 * @since 1.4.0
					 *
					 * @param int $level Debug level passed to PHPMailer::$SMTPDebug. Default 3.
					 */
					$this->SMTPDebug = apply_filters( 'wp_mail_smtp_admin_test_email_smtp_debug', 3 );
				} else {
					$this->SMTPDebug = 3;
				}
			}

/**
			 * Fires before email pre send via SMTP.
			 *
			 * Allow to hook early to catch any early failed emails.
			 *
			 * @since 2.9.0
			 *
			 * @param MailCatcherInterface $mailcatcher The MailCatcher object.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_smtp_pre_send_before', $this );

// Prepare all the headers.
			if ( ! $this->preSend() ) {
				$this->throw_exception( $this->ErrorInfo );
			}

/**
			 * Fires before email send via SMTP.
			 *
			 * Allow to hook after all the preparation before the actual sending.
			 *
			 * @since 2.9.0
			 *
			 * @param MailCatcherInterface $mailcatcher The MailCatcher object.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_smtp_send_before', $this );

if ( ! $this->postSend() ) {
				$this->throw_exception( $this->ErrorInfo );
			}

// PHPMailer's mailSend()/sendmailSend() can return true under SingleTo=true even
			// when individual recipients failed - the result variable is overwritten each loop.
			// Route those through the existing catch by throwing here.
			if ( ! empty( $this->failed_recipients ) ) {
				$failed = array_unique( $this->failed_recipients );

$this->throw_exception(
					sprintf(
						esc_html(
							/* translators: 1: count of failed recipients, 2: comma-separated email addresses. */
							_n(
								'The mail transport accepted the message but rejected %1$d recipient address: %2$s. Other recipients in the same email have been sent.',
								'The mail transport accepted the message but rejected %1$d recipient addresses: %2$s. Other recipients in the same email have been sent.',
								count( $failed ),
								'wp-mail-smtp'
							)
						),
						count( $failed ),
						implode( ', ', $failed )
					)
				);
			}

DebugEvents::add_debug(
				esc_html__( 'An email request was sent.', 'wp-mail-smtp' )
			);

/**
			 * Fires after a successful SMTP/PHP-mail send.
			 *
			 * @since 1.5.0
			 * @since 4.9.0 Fires exactly once per send and only on success.
			 *
			 * @param bool   $is_sent Always true. Kept for backwards-compatible signature.
			 * @param array  $to      To recipients.
			 * @param array  $cc      CC recipients.
			 * @param array  $bcc     BCC recipients.
			 * @param string $subject Email subject.
			 * @param string $body    MIME-encoded body.
			 * @param string $from    From address.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_smtp_send_after', true, $this->to, $this->cc, $this->bcc, $this->Subject, $this->MIMEBody, $this->From );

return true;
		} catch ( Exception $e ) {
			$this->mailHeader = '';

// We need this to append SMTP error to the `PHPMailer::ErrorInfo` property.
			$this->setError( $e->getMessage() );

$error_message = 'Mailer: ' . esc_html( wp_mail_smtp()->get_providers()->get_options( $mailer_slug )->get_title() ) . "\r\n" . $this->ErrorInfo;
			$error_code    = $this->get_smtp_error_code();
			$error_key     = $this->build_error_key( '', $error_code, $this->ErrorInfo ); // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase

$this->latest_error = $error_message;

$debug_event_message = $error_message;
			$debug_output        = implode( "\r\n", $this->debug_output_buffer );

if ( DebugEvents::is_debug_enabled() && ! empty( $debug_output ) ) {
				$debug_event_message .= "\r\n" . esc_html__( 'SMTP Debug:', 'wp-mail-smtp' ) . "\r\n";
				$debug_event_message .= $debug_output;
			}

$this->debug_event_id = DebugEvents::add( $debug_event_message );

$this->record_send_failure( $connection, $mailer_slug, $error_code, $this->ErrorInfo, $this->debug_event_id, $debug_output, $error_key );

/**
			 * Fires after email sent failure via SMTP.
			 *
			 * @since 3.5.0
			 *
			 * @param string               $error_message Error message.
			 * @param MailCatcherInterface $mailcatcher   The MailCatcher object.
			 * @param string               $mailer_slug   Current mailer name.
			 * @param string               $error_code    Error code/slug.
			 * @param int                  $response_code HTTP/SMTP response code (0 for non-API mailers).
			 * @param ConnectionInterface  $connection    The connection object.
			 * @param string               $error_key     Composite error key.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_send_failed', $this->ErrorInfo, $this, $mailer_slug, $error_code, 0, $connection, $error_key );

if ( $this->exceptions ) {
				throw $e;
			}

return false;
		} finally {

// Clear debug output buffer.
			$this->debug_output_buffer = [];
		}
		// phpcs:enable WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
	}

/**
	 * Send email via API integration.
	 *
	 * @since 4.0.0
	 *
	 * @param ConnectionInterface $connection The connection object.
	 *
	 * @throws Exception When sending fails for some reason.
	 *
	 * @return bool
	 */
	private function api_send( $connection ) { // phpcs:ignore Generic.Metrics.CyclomaticComplexity.TooHigh

$mailer_slug = $connection->get_mailer_slug();

// phpcs:disable WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
		try {
			// We need this so that the \PHPMailer class will correctly prepare all the headers.
			$this->Mailer = 'mail';

/**
			 * Fires before email pre send.
			 *
			 * Allow to hook early to catch any early failed emails.
			 *
			 * @since 2.9.0
			 *
			 * @param MailCatcherInterface $mailcatcher The MailCatcher object.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_pre_send_before', $this );

// Prepare everything (including the message) for sending.
			if ( ! $this->preSend() ) {
				$this->throw_exception( $this->ErrorInfo );
			}

$mailer = wp_mail_smtp()->get_providers()->get_mailer( $mailer_slug, $this, $connection );

if ( ! $mailer ) {
				$this->throw_exception( 'The selected mailer not found.' );
			}

if ( ! $mailer->is_php_compatible() ) {
				$this->throw_exception( 'The selected mailer is not compatible with your PHP version.' );
			}

/**
			 * Fires before email send.
			 *
			 * Allows to hook after all the preparation before the actual sending.
			 *
			 * @since 3.3.0
			 *
			 * @param MailerAbstract $mailer The Mailer object.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_send_before', $mailer );

/*
			 * Send the actual email.
			 * We reuse everything, that was preprocessed for usage in \PHPMailer.
			 */
			$mailer->send();

$is_sent = $mailer->is_email_sent();

/**
			 * Fires after email send.
			 *
			 * Allow to perform any actions with the data.
			 *
			 * @since 3.5.0
			 *
			 * @param MailerAbstract       $mailer      The Mailer object.
			 * @param MailCatcherInterface $mailcatcher The MailCatcher object.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_send_after', $mailer, $this );

if ( $is_sent !== true ) {
				$this->throw_exception( $mailer->get_response_error() );
			}

return true;
		} catch ( Exception $e ) {
			// Add mailer to the beginning and save to display later.
			$message = 'Mailer: ' . esc_html( wp_mail_smtp()->get_providers()->get_options( $mailer_slug )->get_title() ) . "\r\n";

$error_code           = ! empty( $mailer ) ? $mailer->get_response_error_code() : '';
			$response_code        = ! empty( $mailer ) ? $mailer->get_response_code() : 0;
			$error_key            = $this->build_error_key( $response_code > 0 ? (string) $response_code : '', $error_code, $e->getMessage() );
			$error_message        = $message . $e->getMessage();
			$this->debug_event_id = DebugEvents::add( $error_message );
			$this->latest_error   = $error_message;

$this->record_send_failure( $connection, $mailer_slug, $error_code, $e->getMessage(), $this->debug_event_id, '', $error_key );

/**
			 * Fires after email sent failure.
			 *
			 * @since 3.5.0
			 *
			 * @param string               $error_message Error message.
			 * @param MailCatcherInterface $mailcatcher   The MailCatcher object.
			 * @param string               $mailer_slug   Current mailer name.
			 * @param string               $error_code    Error code/slug.
			 * @param int                  $response_code HTTP response code.
			 * @param ConnectionInterface  $connection    The connection object.
			 * @param string               $error_key     Composite error key.
			 */
			do_action( 'wp_mail_smtp_mailcatcher_send_failed', $e->getMessage(), $this, $mailer_slug, $error_code, $response_code, $connection, $error_key );

if ( $this->exceptions ) {
				throw $e;
			}

return false;
		}
		// phpcs:enable WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
	}

/**
	 * Create a unique ID to use for multipart email boundaries.
	 *
	 * @since 2.4.0
	 *
	 * @return string
	 */
	public function generate_id() {

return $this->generateId();
	}

/**
	 * Get SMTP error code combining error category and numeric SMTP code.
	 *
	 * Reverse-lookups PHPMailer language key from ErrorInfo via static::$language,
	 * making the category language-independent even if PHPMailer is translated (WP 6.8+).
	 *
	 * @since 4.8.0
	 *
	 * @return string Error code like "authenticate_535", "connect_host", or empty.
	 */
	private function get_smtp_error_code() {

$smtp_code = $this->last_error_code;
		$category  = '';

// Reverse-lookup PHPMailer language key from ErrorInfo.
		// Use getTranslations() which works in both old (instance $language) and new (static $language) PHPMailer.
		$language = method_exists( $this, 'getTranslations' ) ? $this->getTranslations() : [];

foreach ( $language as $key => $translated ) { // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
			if ( ! empty( $translated ) && strpos( $this->ErrorInfo, $translated ) === 0 ) { // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
				$category = $key;

break;
			}
		}

$parts = array_filter( [ $category, $smtp_code ] );

return ! empty( $parts ) ? implode( '_', $parts ) : '';
	}

/**
	 * Build the composite error key: {prefix}:{error_code}:{sanitized_message}.
	 *
	 * Mirrors ErrorStats::build_error_key() for valid inputs; guards mbstring and
	 * null-coalesces preg results so it cannot throw on the send-failure path.
	 *
	 * @since 4.9.0
	 *
	 * @param string $prefix        HTTP response code or category (e.g. "401", "delivery").
	 * @param string $error_code    Provider/SMTP error code.
	 * @param string $error_message Error message text.
	 *
	 * @return string
	 */
	private function build_error_key( $prefix, $error_code, $error_message ) { // phpcs:ignore Generic.Metrics.CyclomaticComplexity.TooHigh

$max_length    = 50;
		$part_response = ! empty( $prefix ) ? $prefix : '-';
		$part_code     = ! empty( $error_code ) && $error_code !== 'unknown' && (string) $error_code !== $part_response ? $error_code : '-';
		$part_message  = ! empty( $error_message ) ? $this->sanitize_error_message( $error_message ) : '-';

if ( $part_response !== '-' ) {
			$part_message = str_replace( sanitize_title( $part_response ), '', $part_message );
		}

if ( $part_code !== '-' ) {
			$part_message = str_replace( sanitize_title( $part_code ), '', $part_message );
		}

$part_message = (string) preg_replace( '/-{2,}/', '-', $part_message );
		$part_message = trim( $part_message, '-' );

if ( empty( $part_message ) ) {
			$part_message = '-';
		}

$key = $part_response . ':' . $part_code . ':' . $part_message;

// function_exists guard so a missing mbstring extension can never fatal on
		// the send path; substr is an exact byte fallback for this ASCII key.
		$key_length = function_exists( 'mb_strlen' ) ? mb_strlen( $key ) : strlen( $key );

if ( $key_length > $max_length ) {
			$key = function_exists( 'mb_substr' ) ? mb_substr( $key, 0, $max_length ) : substr( $key, 0, $max_length );

$last_hyphen = strrpos( $key, '-' );

if ( $last_hyphen !== false && $last_hyphen > strrpos( $key, ':' ) ) {
				$key = substr( $key, 0, $last_hyphen );
			}
		}

return $key;
	}

/**
	 * Sanitize an error message into a short aggregatable slug.
	 *
	 * Mirrors ErrorStats::sanitize_message() with null-safe casts.
	 *
	 * @since 4.9.0
	 *
	 * @param string $message Error message.
	 *
	 * @return string
	 */
	private function sanitize_error_message( $message ) {

$message = html_entity_decode( $message, ENT_QUOTES, 'UTF-8' );
		$message = (string) preg_replace( '/\S+@\S+\.\S+/', '', $message );
		$message = (string) preg_replace( '#https?://\S+#i', '', $message );
		$message = (string) preg_replace( '/\b\S+\.\S+\b/', '', $message );
		$message = (string) preg_replace( '/[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/i', '', $message );
		$message = (string) preg_replace( '/["\'][^"\']*["\']/', '', $message );
		$message = trim( (string) preg_replace( '/\s+/', ' ', $message ) );

return sanitize_title( $message );
	}

/**
	 * Write a failure record into EmailSendingDebug for the given connection.
	 *
	 * Shared between the SMTP and API catch paths - per-path values (error message,
	 * error code, debug event id) are computed locally and passed in.
	 *
	 * Also snapshots the environment data the failure-display layer needs to
	 * reconstruct a full debug bundle later (WP/PHP/plugin versions, multisite flag,
	 * settings-as-constants flag, plugin conflicts, mailer-specific debug info, and
	 * the captured SMTPDebug output). Capturing these at write-time matters because
	 * they reflect server state at the moment of failure (conflicts, constants
	 * enabled) and PHPMailer's transient SMTPDebug buffer is gone after the send.
	 *
	 * @since 4.9.0
	 *
	 * @param ConnectionInterface $connection     Mail connection the failure belongs to.
	 * @param string              $mailer_slug    Current mailer slug.
	 * @param string              $error_code     Provider/SMTP-specific error code.
	 * @param string              $error_message  Human-readable error message.
	 * @param int|false           $debug_event_id DebugEvents row id for this failure, or false when none.
	 * @param string              $smtp_debug     Captured PHPMailer SMTPDebug output, or empty string when none.
	 * @param string              $error_key      Composite error key, or empty string when not yet built.
	 */
	private function record_send_failure( $connection, $mailer_slug, $error_code, $error_message, $debug_event_id, $smtp_debug = '', $error_key = '' ) {

$initiator          = wp_mail_smtp()->get_wp_mail_initiator();
		$connection_options = $connection->get_options();
		$conflicts          = new Conflicts();
		$mailer             = wp_mail_smtp()->get_providers()->get_mailer( $mailer_slug, $this, $connection );

EmailSendingDebug::set(
			$connection->get_id(),
			[
				'occurred_at'       => time(),
				'context'           => ( $this->is_test_email() || $this->is_setup_wizard_test_email() ) ? 'test' : 'regular',
				'status'            => 'failed',
				'mailer'            => $mailer_slug,
				'error_code'        => $error_code,
				'error_key'         => $error_key,
				'error_message'     => $error_message,
				'initiator_name'    => $initiator->get_name(),
				'initiator_file'    => $initiator->get_file() . ':' . $initiator->get_line(),
				'debug_event_id'    => $debug_event_id,
				'wp_version'        => get_bloginfo( 'version' ),
				'is_multisite'      => is_multisite(),
				'php_version'       => PHP_VERSION,
				'plugin_version'    => WPMS_PLUGIN_VER,
				'constants_enabled' => $connection_options->is_const_enabled(),
				'conflicts'         => $conflicts->is_detected() ? $conflicts->get_all_conflict_names() : [],
				'mailer_debug_info' => $mailer ? $mailer->get_debug_info() : '',
				'smtp_debug_info'   => $smtp_debug,
			]
		);
	}

/**
	 * Override setError to capture SMTP error codes before PHPMailer clears them.
	 *
	 * PHPMailer's SMTP quit() clears the error via sendCommand success.
	 * By the time we catch the exception, the SMTP error code is gone.
	 * Uses first-write-wins so subsequent setError calls (RSET, connect_host fallback)
	 * cannot overwrite the original meaningful code.
	 *
	 * @since 4.8.0
	 *
	 * @param string $msg Error message.
	 */
	protected function setError( $msg ) { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid

// Capture SMTP error code with first-write-wins before quit() wipes it.
		if (
			empty( $this->last_error_code ) &&
			isset( $this->smtp ) &&
			$this->smtp instanceof \PHPMailer\PHPMailer\SMTP
		) {
			$error = $this->smtp->getError();

if ( ! empty( $error['smtp_code'] ) ) {
				$this->last_error_code = (string) $error['smtp_code'];
			}
		}

parent::setError( $msg );
	}

/**
	 * Override PHPMailer's per-send callback fan-out.
	 *
	 * PHPMailer dispatches this once per recipient in smtpSend(), and once per
	 * recipient under SingleTo=true in mailSend()/sendmailSend(). We collect failed
	 * recipient addresses and let smtp_send() decide once, at the end, whether the
	 * overall send succeeded.
	 *
	 * @since 4.9.0
	 *
	 * @param bool         $is_sent Whether PHPMailer accepted this recipient.
	 * @param array|string $to      Recipients for this callback (single recipient in
	 *                              the per-recipient paths; full list in default mailSend).
	 * @param array        $cc      CC addresses (unused).
	 * @param array        $bcc     BCC addresses (unused).
	 * @param string       $subject Subject (unused).
	 * @param string       $body    Body (unused).
	 * @param string       $from    From address (unused).
	 * @param array        $extra   Extra data (unused).
	 */
	protected function doCallback( $is_sent, $to, $cc, $bcc, $subject, $body, $from, $extra ) { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid, WordPress.NamingConventions.ValidVariableName.VariableNotSnakeCase

if ( $is_sent ) {
			return;
		}

// $to is an array of [email, name] tuples; $recipient[0] is the email field of
		// the current tuple, not the first recipient. Loop captures every failed address.
		foreach ( (array) $to as $recipient ) {
			if ( is_array( $recipient ) && isset( $recipient[0] ) && is_string( $recipient[0] ) && $recipient[0] !== '' ) {
				$this->failed_recipients[] = $recipient[0];
			} elseif ( is_string( $recipient ) && $recipient !== '' ) {
				$this->failed_recipients[] = $recipient;
			}
		}
	}

/**
	 * Debug output callback.
	 * Save debugging info to buffer array.
	 *
	 * @since 3.3.0
	 *
	 * @param string $str   Message.
	 * @param int    $level Debug level.
	 */
	public function debug_output_callback( $str, $level ) {

/*
		 * Filter out all higher levels than 3.
		 * SMTPDebug level 3 is commands, data and connection status.
		 */
		if ( $level > 3 ) {
			return;
		}

$this->debug_output_buffer[] = trim( $str, "\r\n" );
	}

/**
	 * Get debug event ID.
	 *
	 * @since 3.5.0
	 *
	 * @return bool|int
	 */
	public function get_debug_event_id() {

return $this->debug_event_id;
	}

/**
	 * Whether the current email is a test email.
	 *
	 * @since 3.5.0
	 *
	 * @return bool
	 */
	public function is_test_email() {

return $this->is_test_email;
	}

/**
	 * Whether the current email is a Setup Wizard test email.
	 *
	 * @since 3.5.0
	 *
	 * @return bool
	 */
	public function is_setup_wizard_test_email() {

return $this->is_setup_wizard_test_email;
	}

/**
	 * Whether the current email is blocked to be sent.
	 *
	 * @since 3.8.0
	 *
	 * @return bool
	 */
	public function is_emailing_blocked() {

return $this->is_emailing_blocked;
	}

/**
	 * Return the list of properties representing
	 * this class' state.
	 *
	 * @since 4.0.0
	 *
	 * @return array State of this class.
	 */
	private function get_state_properties() {

return [
			'CharSet',
			'ContentType',
			'Encoding',
			'CustomHeader',
			'Subject',
			'Body',
			'AltBody',
			'ReplyTo',
			'to',
			'cc',
			'bcc',
			'attachment',
		];
	}

/**
	 * Return an array of relevant properties.
	 *
	 * @since 4.0.0
	 *
	 * @return array State of this class.
	 */
	public function get_state() {

$state = [];

foreach ( $this->get_state_properties() as $property ) {
			$state[ $property ] = $this->{$property};
		}

return $state;
	}

/**
	 * Set properties from a provided array of data.
	 *
	 * @since 4.0.0
	 *
	 * @param array $state Array of properties to apply.
	 */
	public function set_state( $state ) { // phpcs:ignore Generic.Metrics.NestingLevel.MaxExceeded

// Filter out non-allowed properties.
		$state = array_intersect_key(
			$state,
			array_flip( $this->get_state_properties() )
		);

foreach ( $state as $property => $value ) {
			if ( $property !== 'attachment' ) {
				$this->{$property} = $value;
			} else {
				// Handle potential I/O exceptions
				// in PHPMailer when attaching files.
				$this->clearAttachments();

foreach ( $state['attachment'] as $attachment ) {
					[ $path, , $name ] = $attachment;

try {
						$this->addAttachment( $path, $name );
					} catch ( Exception $e ) {
						continue;
					}
				}
			}
		}
	}

/**
	 * Set the From and FromName properties.
	 *
	 * @since 4.7.1
	 *
	 * @param string $address Email address.
	 * @param string $name    Name.
	 * @param bool   $auto    Whether to also set the Sender address, defaults to true.
	 *
	 * @return bool Returns true on success and false on failure.
	 */
	public function setFrom( $address, $name = '', $auto = true ) { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid

// Set `$auto` param as false, to control return-path via plugin settings.
		return parent::setFrom( $address, $name, false );
	}
}