This commit is contained in:
Javier Casares 2026-01-29 10:02:03 +00:00
commit a29b2d82ad
19 changed files with 3792 additions and 231 deletions

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<?php
/**
* Amazon SES Mailer.
*
* @package ROBOTSTXT_SMTP_Newsletter
*/
namespace Robotstxt_SMTP_Newsletter;
if ( ! defined( 'ABSPATH' ) ) {
exit;
}
/**
* Amazon SES Mailer class.
*
* Implements batch email sending using Amazon SES API.
*/
class AmazonSES_Mailer extends \NewsletterMailer {
/**
* SES client instance.
*
* @var \Aws\SesV2\SesV2Client|null
*/
private $ses_client = null;
/**
* SMTP settings from robotstxt-smtp plugin.
*
* @var array<string, mixed>
*/
private $settings = array();
/**
* Batch size for bulk sending.
*
* @var int
*/
protected $batch_size = 50;
/**
* Constructor.
*
* @param array<string, mixed> $options Plugin options.
*/
public function __construct( $options = array() ) {
parent::__construct( 'robotstxt-smtp-newsletter', $options );
$this->settings = Plugin::get_instance()->get_smtp_settings();
// Configure batch_size from turbo (standard Newsletter pattern).
// SES can handle larger batches than SMTP.
if ( ! empty( $options['turbo'] ) ) {
$this->batch_size = max( 1, (int) $options['turbo'] );
}
}
/**
* Get speed (emails per hour) for Newsletter engine.
*
* Standard Newsletter addons don't implement this, but we do
* to allow dynamic speed calculation based on rate limits.
*
* @return int
*/
public function get_speed() {
return $this->speed;
}
/**
* Get SES client instance.
*
* @return \Aws\SesV2\SesV2Client
* @throws \Exception If SES client cannot be initialized.
*/
private function get_ses_client() {
if ( $this->ses_client !== null ) {
return $this->ses_client;
}
if ( ! class_exists( '\Robotstxt_SMTP_AmazonSES\Plugin' ) ) {
throw new \Exception( __( 'Amazon SES plugin not available.', 'robotstxt-smtp-newsletter' ) );
}
$ses_plugin = \Robotstxt_SMTP_AmazonSES\Plugin::get_instance();
$this->ses_client = $ses_plugin->get_ses_client(
$this->settings['amazon_ses_access_key'],
$this->settings['amazon_ses_secret_key'],
$this->settings['amazon_ses_region']
);
return $this->ses_client;
}
/**
* Send single email via SES API.
*
* @param \TNP_Mailer_Message $message Message to send.
*
* @return bool|WP_Error True on success, WP_Error on failure.
*/
public function send( $message ) {
try {
$client = $this->get_ses_client();
// Check rate limits BEFORE sending.
if ( ! $this->check_rate_limits() ) {
return new \WP_Error(
self::ERROR_FATAL,
__( 'Rate limit exceeded. Please wait before sending more emails.', 'robotstxt-smtp-newsletter' )
);
}
$params = $this->prepare_ses_params( $message );
$result = $client->sendEmail( $params );
// Track rate limit.
$this->track_email_sent();
return true;
} catch ( \Aws\Exception\AwsException $e ) {
$this->log_error( $message, $e->getAwsErrorMessage() );
return new \WP_Error( self::ERROR_GENERIC, $e->getAwsErrorMessage() );
} catch ( \Exception $e ) {
$this->log_error( $message, $e->getMessage() );
return new \WP_Error( self::ERROR_GENERIC, $e->getMessage() );
}
}
/**
* Send chunk of emails via SES API.
*
* Note: SES API doesn't have batch endpoint, so we send sequentially.
* However, API calls are much faster than SMTP connections.
*
* @param array<\TNP_Mailer_Message> $messages Messages to send.
*
* @return bool|WP_Error True on success, WP_Error on fatal error.
*/
public function send_chunk( $messages ) {
$undelivered = 0;
$fatal_error = null;
foreach ( $messages as $message ) {
try {
$client = $this->get_ses_client();
// Check rate limits.
if ( ! $this->check_rate_limits() ) {
$message->error = __( 'Rate limit exceeded', 'robotstxt-smtp-newsletter' );
$fatal_error = new \WP_Error(
self::ERROR_FATAL,
__( 'Rate limit exceeded. Batch stopped.', 'robotstxt-smtp-newsletter' )
);
break; // Stop on rate limit.
}
$params = $this->prepare_ses_params( $message );
$result = $client->sendEmail( $params );
// Track rate limit.
$this->track_email_sent();
} catch ( \Aws\Exception\AwsException $e ) {
$this->log_error( $message, $e->getAwsErrorMessage() );
$message->error = $e->getAwsErrorMessage();
++$undelivered;
// Only stop on critical AWS errors (credentials, rate limits).
// Continue sending if only individual recipient failed (bounce, suppress list).
$error_code = $e->getAwsErrorCode();
$is_fatal = in_array(
$error_code,
array( 'InvalidClientTokenId', 'SignatureDoesNotMatch', 'Throttling', 'RequestExpired' ),
true
);
if ( $is_fatal ) {
$fatal_error = new \WP_Error( self::ERROR_FATAL, $e->getAwsErrorMessage() );
break; // Stop batch on critical errors.
}
// Otherwise continue with next recipient.
} catch ( \Exception $e ) {
$this->log_error( $message, $e->getMessage() );
$message->error = $e->getMessage();
++$undelivered;
// On unexpected errors, stop the batch.
$fatal_error = new \WP_Error( self::ERROR_FATAL, $e->getMessage() );
break;
}
}
if ( $fatal_error ) {
return $fatal_error;
}
if ( $undelivered > 0 ) {
return new \WP_Error( self::ERROR_GENERIC, sprintf( '%d emails undelivered', $undelivered ) );
}
return true;
}
/**
* Prepare SES API parameters from message.
*
* @param \TNP_Mailer_Message $message Message to prepare.
*
* @return array<string, mixed> SES API parameters.
*/
private function prepare_ses_params( $message ) {
$params = array(
'FromEmailAddress' => ! empty( $message->from_name )
? sprintf( '%s <%s>', $message->from_name, $message->from )
: $message->from,
'Destination' => array(
'ToAddresses' => array( $message->to ),
),
'Content' => array(
'Simple' => array(
'Subject' => array(
'Data' => $message->subject,
'Charset' => 'UTF-8',
),
'Body' => array(),
),
),
);
// Add HTML body.
if ( ! empty( $message->body ) ) {
$params['Content']['Simple']['Body']['Html'] = array(
'Data' => $message->body,
'Charset' => 'UTF-8',
);
}
// Add text body.
if ( ! empty( $message->body_text ) ) {
$params['Content']['Simple']['Body']['Text'] = array(
'Data' => $message->body_text,
'Charset' => 'UTF-8',
);
}
// Reply-To.
if ( ! empty( $this->settings['reply_to_email'] ) ) {
$params['ReplyToAddresses'] = array( $this->settings['reply_to_email'] );
}
// Custom headers.
if ( ! empty( $message->headers ) && is_array( $message->headers ) ) {
$email_headers = array();
foreach ( $message->headers as $key => $value ) {
$email_headers[] = array(
'Name' => $key,
'Value' => $value,
);
}
if ( ! empty( $email_headers ) ) {
$params['Content']['Raw'] = array(
'Data' => $this->build_raw_message( $message, $email_headers ),
);
unset( $params['Content']['Simple'] );
}
}
return $params;
}
/**
* Build raw MIME message for custom headers.
*
* @param \TNP_Mailer_Message $message Message.
* @param array<array> $headers Custom headers.
*
* @return string Base64-encoded raw message.
*/
private function build_raw_message( $message, $headers ) {
// This is a simplified implementation.
// For production, consider using a proper MIME builder.
$raw = "From: {$message->from}\r\n";
$raw .= "To: {$message->to}\r\n";
$raw .= "Subject: {$message->subject}\r\n";
foreach ( $headers as $header ) {
$raw .= "{$header['Name']}: {$header['Value']}\r\n";
}
$raw .= "MIME-Version: 1.0\r\n";
$raw .= "Content-Type: text/html; charset=UTF-8\r\n\r\n";
$raw .= $message->body;
return base64_encode( $raw );
}
/**
* Check rate limits using SES quotas.
*
* @return bool True if sending is allowed, false otherwise.
*/
private function check_rate_limits() {
// Rate limiting will be implemented using SES quota integration.
// For now, return true to allow sending.
// TODO: Integrate with robotstxt-smtp-amazonses quota checking.
return true;
}
/**
* Track sent email for rate limiting.
*
* @return void
*/
private function track_email_sent() {
// Track email for rate limiting.
// TODO: Integrate with robotstxt-smtp rate limiting tracking.
}
/**
* Log error to Newsletter system.
*
* @param \TNP_Mailer_Message $message Message that failed.
* @param string $error_message Error message.
*
* @return void
*/
private function log_error( $message, $error_message ) {
error_log(
sprintf(
'ROBOTSTXT SMTP Newsletter (SES): Failed to send to %s. Error: %s',
$message->to,
$error_message
)
);
if ( $logger ) {
$logger->error(
sprintf(
'Amazon SES: Failed to send to %s. Error: %s',
$message->to,
$error_message
)
);
}
}
}
}

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<?php
/**
* Main plugin class.
*
* @package ROBOTSTXT_SMTP_Newsletter
*/
namespace Robotstxt_SMTP_Newsletter;
if ( ! defined( 'ABSPATH' ) ) {
exit;
}
/**
* Plugin main class.
*
* Extends NewsletterMailerAddon to integrate with Newsletter plugin.
*/
class Plugin extends \NewsletterMailerAddon {
/**
* Singleton instance.
*
* @var Plugin|null
*/
private static $instance = null;
/**
* Default options.
*
* @var array<string, mixed>
*/
private static $defaults = array(
'enabled' => false,
'batch_size' => 10,
'max_per_connection' => 50,
);
/**
* Plugin display name.
*
* @var string
*/
public $name;
/**
* Plugin slug.
*
* @var string
*/
public $slug;
/**
* Menu title.
*
* @var string
*/
public $menu_title;
/**
* Get singleton instance.
*
* @return Plugin
*/
public static function get_instance() {
if ( null === self::$instance ) {
self::$instance = new self();
}
return self::$instance;
}
/**
* Initialize plugin (called on newsletter_loaded hook).
*
* @return void
*/
public static function instance_init() {
$instance = self::get_instance();
$instance->init();
}
/**
* Constructor.
*/
private function __construct() {
parent::__construct( 'robotstxt-smtp-newsletter', ROBOTSTXT_SMTP_NEWSLETTER_VERSION, ROBOTSTXT_SMTP_NEWSLETTER_PATH );
$this->name = 'SMTP (by ROBOTSTXT)';
$this->slug = 'robotstxt-smtp-newsletter';
$this->menu_title = 'SMTP (by ROBOTSTXT)';
}
/**
* Setup options.
*
* Overrides parent to use our custom option name.
*
* @return void
*/
public function setup_options() {
if ( $this->options ) {
return;
}
// Load our options using our custom option name (not newsletter_ prefix).
$this->options = get_option( 'robotstxt_smtp_newsletter_options', array() );
$this->options = wp_parse_args( $this->options, self::$defaults );
}
/**
* Initialize plugin hooks.
*
* Overrides parent init() method.
*
* @return void
*/
public function init() {
parent::init();
// Load text domain.
add_action( 'init', array( $this, 'load_textdomain' ) );
// Register settings (but not menu - parent handles that).
if ( is_admin() ) {
require_once ROBOTSTXT_SMTP_NEWSLETTER_PATH . 'admin/class-settings-page.php';
add_action( 'admin_init', array( 'Robotstxt_SMTP_Newsletter\Admin\Settings_Page', 'register_settings_static' ) );
}
}
/**
* Load plugin text domain for translations.
*
* @return void
*/
public function load_textdomain() {
load_plugin_textdomain(
'robotstxt-smtp-newsletter',
false,
dirname( plugin_basename( ROBOTSTXT_SMTP_NEWSLETTER_FILE ) ) . '/languages'
);
}
/**
* Get the mailer instance.
*
* This method is called by the parent class to get the mailer
* that should be registered with Newsletter.
*
* @return \NewsletterMailer
*/
public function get_mailer() {
// Get our settings and map to Newsletter's expected format.
$settings = $this->get_settings();
$smtp_settings = $this->get_smtp_settings();
// Calculate optimal speed (emails per hour) based on rate limits.
$speed = $this->calculate_optimal_speed( $smtp_settings );
// Newsletter expects 'turbo' for batch_size and 'speed' for emails/hour.
$mailer_options = array(
'turbo' => $settings['batch_size'] ?? 10,
'speed' => $speed,
'max_per_connection' => $settings['max_per_connection'] ?? 50,
);
// Detect if Amazon SES is active.
if ( $this->is_amazon_ses_active() ) {
require_once ROBOTSTXT_SMTP_NEWSLETTER_PATH . 'includes/class-amazonses-mailer.php';
return new AmazonSES_Mailer( $mailer_options );
} else {
require_once ROBOTSTXT_SMTP_NEWSLETTER_PATH . 'includes/class-smtp-mailer.php';
return new SMTP_Mailer( $mailer_options );
}
}
/**
* Calculate optimal speed (emails per hour) based on rate limits.
*
* @param array<string, mixed> $smtp_settings SMTP settings with rate limits.
*
* @return int Emails per hour.
*/
private function calculate_optimal_speed( $smtp_settings ) {
// Get rate limits from ROBOTSTXT SMTP settings.
$rate_per_hour = absint( $smtp_settings['rate_limit_per_hour'] ?? 0 );
// If hourly limit is set, use it (with 90% safety margin).
if ( $rate_per_hour > 0 ) {
return (int) floor( $rate_per_hour * 0.9 );
}
// If no hourly limit, calculate from per-second limit.
$rate_per_second = absint( $smtp_settings['rate_limit_per_second'] ?? 0 );
if ( $rate_per_second > 0 ) {
return (int) floor( $rate_per_second * 3600 * 0.9 );
}
// If no limits set, use a conservative default based on delivery method.
$is_ses = $this->is_amazon_ses_active();
return $is_ses ? 1000 : 500;
}
/**
* Check if Amazon SES integration is active.
*
* @return bool
*/
private function is_amazon_ses_active() {
if ( ! class_exists( '\Robotstxt_SMTP\Plugin' ) ) {
return false;
}
return \Robotstxt_SMTP\Plugin::is_amazon_ses_integration_active();
}
/**
* Get plugin settings with defaults.
*
* @return array<string, mixed>
*/
public function get_settings() {
$options = get_option( 'robotstxt_smtp_newsletter_options', array() );
return wp_parse_args( $options, self::$defaults );
}
/**
* Get SMTP settings from robotstxt-smtp plugin.
*
* @return array<string, mixed>
*/
public function get_smtp_settings() {
if ( ! class_exists( '\Robotstxt_SMTP\Plugin' ) || ! class_exists( '\Robotstxt_SMTP\Admin\Settings_Page' ) ) {
return array();
}
// Check if network mode is enabled.
$scope = get_site_option( 'robotstxt_smtp_configuration_scope', 'site' );
if ( 'network' === $scope ) {
$settings = get_site_option( 'robotstxt_smtp_network_options', array() );
} else {
$settings = get_option( 'robotstxt_smtp_options', array() );
}
return $settings;
}
}

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<?php
/**
* SMTP Mailer with KeepAlive support.
*
* @package ROBOTSTXT_SMTP_Newsletter
*/
namespace Robotstxt_SMTP_Newsletter;
if ( ! defined( 'ABSPATH' ) ) {
exit;
}
/**
* SMTP Mailer class.
*
* Implements efficient batch email sending using SMTPKeepAlive.
*/
class SMTP_Mailer extends \NewsletterMailer {
/**
* PHPMailer instance with persistent connection.
*
* @var \PHPMailer\PHPMailer\PHPMailer|null
*/
private $phpmailer = null;
/**
* SMTP settings from robotstxt-smtp plugin.
*
* @var array<string, mixed>
*/
private $settings = array();
/**
* Batch size for bulk sending.
*
* @var int
*/
protected $batch_size = 10;
/**
* Maximum emails per connection before reconnecting.
*
* @var int
*/
private $max_emails_per_connection = 50;
/**
* Count of emails sent in current connection.
*
* @var int
*/
private $emails_sent_in_connection = 0;
/**
* Constructor.
*
* @param array<string, mixed> $options Plugin options.
*/
public function __construct( $options = array() ) {
parent::__construct( 'robotstxt-smtp-newsletter', $options );
$this->settings = Plugin::get_instance()->get_smtp_settings();
// Configure batch_size from turbo (standard Newsletter pattern).
if ( ! empty( $options['turbo'] ) ) {
$this->batch_size = max( 1, (int) $options['turbo'] );
}
$this->max_emails_per_connection = max( 1, (int) ( $options['max_per_connection'] ?? 50 ) );
}
/**
* Get speed (emails per hour) for Newsletter engine.
*
* Standard Newsletter addons don't implement this, but we do
* to allow dynamic speed calculation based on rate limits.
*
* @return int
*/
public function get_speed() {
return $this->speed;
}
/**
* Initialize PHPMailer with SMTPKeepAlive.
*
* @return \PHPMailer\PHPMailer\PHPMailer
* @throws \Exception If PHPMailer cannot be initialized.
*/
private function get_phpmailer() {
if ( $this->phpmailer !== null ) {
return $this->phpmailer;
}
$this->phpmailer = new \PHPMailer\PHPMailer\PHPMailer( true );
// Configure SMTP.
$this->phpmailer->isSMTP();
$this->phpmailer->Host = $this->settings['host'];
$this->phpmailer->Port = $this->settings['port'];
$this->phpmailer->SMTPAuth = ! empty( $this->settings['user'] );
$this->phpmailer->Username = $this->settings['user'];
$this->phpmailer->Password = $this->settings['password'];
// Security.
$encryption = $this->settings['encryption'] ?? '';
if ( 'tls' === $encryption ) {
$this->phpmailer->SMTPSecure = \PHPMailer\PHPMailer\PHPMailer::ENCRYPTION_STARTTLS;
} elseif ( 'ssl' === $encryption ) {
$this->phpmailer->SMTPSecure = \PHPMailer\PHPMailer\PHPMailer::ENCRYPTION_SMTPS;
}
// CRITICAL: Enable KeepAlive for batch sending.
$this->phpmailer->SMTPKeepAlive = true;
// Set HELO hostname using WordPress site URL (works in multisite and WP-CLI).
$site_hostname = wp_parse_url( get_site_url(), PHP_URL_HOST );
if ( $site_hostname ) {
$this->phpmailer->Hostname = $site_hostname;
}
// Additional settings.
$this->phpmailer->Timeout = 30;
$this->phpmailer->SMTPDebug = 0;
$this->phpmailer->CharSet = 'UTF-8';
return $this->phpmailer;
}
/**
* Send single email.
*
* Uses persistent SMTP connection (SMTPKeepAlive) for efficiency.
*
* @param \TNP_Mailer_Message $message Message to send.
*
* @return bool|WP_Error True on success, WP_Error on failure.
*/
public function send( $message ) {
try {
$mailer = $this->get_phpmailer();
// Clear previous message data but keep connection.
$mailer->clearAddresses();
$mailer->clearReplyTos();
$mailer->clearAttachments();
$mailer->clearCustomHeaders();
$this->prepare_message( $mailer, $message );
// Check rate limits BEFORE sending.
if ( ! $this->check_rate_limits() ) {
return new \WP_Error(
self::ERROR_FATAL,
__( 'Rate limit exceeded. Please wait before sending more emails.', 'robotstxt-smtp-newsletter' )
);
}
$mailer->send();
++$this->emails_sent_in_connection;
// Track rate limit.
$this->track_email_sent();
// Reconnect if threshold reached.
if ( $this->emails_sent_in_connection >= $this->max_emails_per_connection ) {
$this->close_connection();
}
return true;
} catch ( \Exception $e ) {
$this->log_error( $message, $e->getMessage() );
return new \WP_Error( self::ERROR_GENERIC, $e->getMessage() );
}
}
/**
* Send chunk of emails using persistent SMTP connection.
*
* Unlike API-based addons that use curl_multi for parallel sending,
* SMTP is sequential but benefits from keeping the connection alive.
*
* @param array<\TNP_Mailer_Message> $messages Messages to send.
*
* @return bool|WP_Error True on success, WP_Error on fatal error.
*/
public function send_chunk( $messages ) {
$mailer = $this->get_phpmailer();
$undelivered = 0;
$fatal_error = null;
foreach ( $messages as $index => $message ) {
try {
// Clear previous message data but keep connection.
$mailer->clearAddresses();
$mailer->clearReplyTos();
$mailer->clearAttachments();
$mailer->clearCustomHeaders();
$this->prepare_message( $mailer, $message );
// Check rate limits.
if ( ! $this->check_rate_limits() ) {
$message->error = __( 'Rate limit exceeded', 'robotstxt-smtp-newsletter' );
$fatal_error = new \WP_Error(
self::ERROR_FATAL,
__( 'Rate limit exceeded. Batch stopped.', 'robotstxt-smtp-newsletter' )
);
break; // Stop on rate limit.
}
$mailer->send();
++$this->emails_sent_in_connection;
$this->track_email_sent();
// Reconnect if threshold reached.
if ( $this->emails_sent_in_connection >= $this->max_emails_per_connection ) {
$this->close_connection();
$mailer = $this->get_phpmailer(); // Get fresh connection.
}
} catch ( \Exception $e ) {
$this->log_error( $message, $e->getMessage() );
$message->error = $e->getMessage();
++$undelivered;
// Only stop on critical SMTP errors (connection, auth).
// Continue sending if only individual recipient failed.
$error_msg = $e->getMessage();
$is_fatal = (
stripos( $error_msg, 'Could not connect' ) !== false ||
stripos( $error_msg, 'MAIL FROM command failed' ) !== false ||
stripos( $error_msg, 'Authentication failed' ) !== false ||
stripos( $error_msg, 'Invalid HELO' ) !== false
);
if ( $is_fatal ) {
$fatal_error = new \WP_Error( self::ERROR_FATAL, $e->getMessage() );
break; // Stop batch on critical errors.
}
// Otherwise continue with next recipient.
}
}
if ( $fatal_error ) {
return $fatal_error;
}
if ( $undelivered > 0 ) {
return new \WP_Error( self::ERROR_GENERIC, sprintf( '%d emails undelivered', $undelivered ) );
}
return true;
}
/**
* Prepare message for sending.
*
* @param \PHPMailer\PHPMailer\PHPMailer $mailer PHPMailer instance.
* @param \TNP_Mailer_Message $message Message to prepare.
*
* @return void
* @throws \PHPMailer\PHPMailer\Exception If preparation fails.
*/
private function prepare_message( $mailer, $message ) {
// Use FROM configured in ROBOTSTXT SMTP plugin (required for SMTP auth).
// Falls back to Newsletter's FROM if not configured.
$from_email = ! empty( $this->settings['from_email'] ) ? $this->settings['from_email'] : $message->from;
$from_name = ! empty( $this->settings['from_name'] ) ? $this->settings['from_name'] : $message->from_name;
$mailer->setFrom( $from_email, $from_name );
$mailer->addAddress( $message->to );
$mailer->Subject = $message->subject;
if ( ! empty( $message->body ) ) {
$mailer->isHTML( true );
$mailer->Body = $message->body;
if ( ! empty( $message->body_text ) ) {
$mailer->AltBody = $message->body_text;
}
} else {
$mailer->isHTML( false );
$mailer->Body = $message->body_text;
}
// Reply-To.
if ( ! empty( $this->settings['reply_to_email'] ) ) {
$mailer->addReplyTo(
$this->settings['reply_to_email'],
$this->settings['reply_to_name'] ?? ''
);
}
// Custom headers.
if ( ! empty( $message->headers ) && is_array( $message->headers ) ) {
foreach ( $message->headers as $key => $value ) {
$mailer->addCustomHeader( $key, $value );
}
}
}
/**
* Check rate limits using robotstxt-smtp logic.
*
* @return bool True if sending is allowed, false otherwise.
*/
private function check_rate_limits() {
// Rate limiting will be implemented using robotstxt-smtp methods.
// For now, return true to allow sending.
// TODO: Integrate with robotstxt-smtp rate limiting system.
return true;
}
/**
* Track sent email for rate limiting.
*
* @return void
*/
private function track_email_sent() {
// Track email for rate limiting.
// TODO: Integrate with robotstxt-smtp rate limiting tracking.
}
/**
* Close SMTP connection.
*
* @return void
*/
private function close_connection() {
if ( $this->phpmailer !== null ) {
$this->phpmailer->smtpClose();
$this->phpmailer = null;
$this->emails_sent_in_connection = 0;
}
}
/**
* Log error to PHP error log.
*
* @param \TNP_Mailer_Message $message Message that failed.
* @param string $error_message Error message.
*
* @return void
*/
private function log_error( $message, $error_message ) {
error_log(
sprintf(
'ROBOTSTXT SMTP Newsletter: Failed to send to %s. Error: %s',
$message->to,
$error_message
)
);
}
/**
* Cleanup on destruction.
*/
public function __destruct() {
$this->close_connection();
}
}