class-quickmailutil.php

<?php
/**
 * Welcome to class-quickmailutil.php.
 *
 * @package QuickMail
 */

/**
 * Quick Mail utility functions for JavaScript and quick-mail-cli.php
 */
class QuickMailUtil {

	/**
	 * Nothing to construct here.
	 */
	public function __construct() { }

	/**
	 * Find system temp path.
	 * test upload_tmp_dir, sys_get_temp_dir().
	 *
	 * @return string path
	 */
	public static function qm_get_temp_path() {
		$path = ini_get( 'upload_tmp_dir' );
		if ( ! empty( $path ) ) {
			return trailingslashit( $path );
		}
		return trailingslashit( sys_get_temp_dir() );
	} // end qm_get_temp_path

	/**
	 * Count input characters without spaces.
	 *
	 * @param string  $text original text.
	 * @param integer $min_len minimum acceptable length.
	 * @param integer $max_len maximum acceptable length.
	 * @return boolean input length
	 */
	public static function check_char_count( $text, $min_len = 1, $max_len = 80 ) {
		$charset = is_multisite() ? get_blog_option( get_current_blog_id(), 'blog_charset', 'UTF-8' ) : get_option( 'blog_charset', 'UTF-8' );

		$len = function_exists( 'mb_strlen' ) ? mb_strlen( $text, $charset ) : strlen( $text );
		if ( $len < $min_len || $len > $max_len ) {
			return false;
		} // end if original string is too short or long

		$content = preg_replace( '/\s/', '', $text );
		$len     = function_exists( 'mb_strlen' ) ? mb_strlen( $content, $charset ) : strlen( $content );
		return ( $len >= $min_len );
	} // end check_char_count

	/**
	 * Find duplicates in array. does not check case.
	 *
	 * @see QuickMailUtil::filter_email_input() for use
	 * @param array $orig_names original names from input.
	 * @return string duplicates
	 * @since 1.4.0
	 */
	public static function qm_find_dups( $orig_names ) {
		$retval   = '';
		$all_dups = array();
		$j        = count( $orig_names );
		for ( $i = 0; $i < $j; $i++ ) {
			$name     = $orig_names[ $i ];
			$your_len = function_exists( 'mb_strlen' ) ? mb_strlen( $name, 'UTF-8' ) : strlen( $name );
			if ( 2 > $your_len ) {
				continue;
			}
			$orig_names[ $i ] = '';
			if ( in_array( $name, $orig_names, true ) ) {
				$all_dups[] = $name;
			}
		} // end foreach
		$dups = array_unique( $all_dups );
		foreach ( $dups as $name ) {
			$hsave   = htmlspecialchars( $name, ENT_HTML5 );
			$retval .= "{$hsave}<br>";
		}

		return $retval;
	} // end qm_find_dups

	/**
	 * Remove invalid email addresses from user input.
	 *
	 * Addresses can be delimited with comma or space.
	 *
	 * @param string $to recipient.
	 * @param string $original user input.
	 * @param string $validate_option Y or N.
	 * @return string filtered string
	 *
	 * @since 1.4.0
	 */
	public static function filter_email_input( $to, $original, $validate_option ) {
		$search         = array( '%40', '%20', '+', ' ', '%2C' );
		$replace        = array( '@', ',', ',', ',', ',' );
		$commas         = strtolower( str_ireplace( $search, $replace, trim( $original ) ) );
		$raw_dup        = strtolower( str_ireplace( $search, $replace, trim( $to ) ) );
		$exploded_names = explode( ',', $commas );
		$all_names      = array_unique( $exploded_names );
		// Check for duplicate recipients.
		$duplicate = self::qm_find_dups( $exploded_names );
		$invalid   = '';
		$retval    = array();
		foreach ( $all_names as $name ) {
			if ( empty( $name ) ) {
				continue;
			} // end if empty

			$hname = htmlspecialchars( html_entity_decode( strip_tags( $name ) ), ENT_QUOTES );
			if ( ! self::qm_valid_email_domain( $name, $validate_option ) ) {
				$invalid .= "{$hname}<br>";
				continue;
			} // end if invalid name

			if ( $name === $raw_dup ) {
				if ( ! strstr( $duplicate, $name ) ) {
					$duplicate .= "{$hname}<br>";
				}
				continue;
			} // end if sender is a recipient

			$retval[] = $name;
		} // end for

		$saved = empty( $retval[0] ) ? '' : implode( ',', $retval );
		if ( ! empty( $invalid ) ) {
			if ( empty( $duplicate ) ) {
				return "{$invalid}\t" . $saved;
			} // end if not duplicate

			return "{$invalid}<br><br>(duplicate):<br>{$duplicate}\t" . $saved;
		} // end if invalid

		if ( ! empty( $duplicate ) ) {
			return " {$duplicate}\t" . $saved;
		} // end if duplicates

		return $saved;
	} // end filter_email_input

	/**
	 * Remove invalid email addresses from user input.
	 *
	 * Addresses can be delimited with comma or space.
	 *
	 * @param string $original original user input.
	 * @return array filtered input
	 * @since 1.4.0
	 */
	public static function filter_user_emails( $original ) {
		$commas = str_replace( ' ', ',', $original );
		$data   = explode( ',', strtolower( $commas ) );
		$retval = array();
		foreach ( $data as $qm_address ) {
			if ( self::qm_valid_email_domain( $qm_address ) ) {
				$retval[] = $qm_address;
			} // end if valid address
		} // end foreach

		return array_unique( $retval );
	} // end filter_user_emails

	/**
	 * Reject arbitrary recipient domains. Uses qm_rejected_domains filter.
	 *
	 * @param string $domain recipient domain.
	 * @return boolean|string empty value is rejected.
	 * @since 4.0.5
	 */
	public static function acceptable_domain( $domain ) {
		$url        = "{$_SERVER['REQUEST_SCHEME']}://{$_SERVER['SERVER_NAME']}/wp-admin/admin-ajax.php";
		$ajax_nonce = wp_create_nonce( 'quick_mail_banned' );
		$args       = array(
			'action'   => 'quick_mail_banned',
			'security' => $ajax_nonce,
			'domain'   => $domain,
		);
		$content    = http_build_query( $args );
		$protocol   = floatval( substr( $_SERVER['SERVER_PROTOCOL'], -3 ) );
		$h1         = "Content-type: application/x-www-form-urlencoded\r\n";
		$dlen       = strlen( $content );
		$h2         = "Content-Length: {$dlen}\r\n";
		$header     = $h1 . $h2;
		$options    = array(
			'http' =>
				array(
					'method'     => 'POST',
					'header'     => $header,
					'user_agent' => 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:84.0) Gecko/20100101 Firefox/84.0',
					'protocol'   => $protocol,
					'content'    => $content,
				),
		);

		$stream_context = stream_context_create( $options );
		$result         = file_get_contents( $url, false, $stream_context );
		if ( false !== $result ) {
			$domain = $result;
		}
		return $domain;
	}

	/**
	 * Validate email domain with DNS record.
	 * Translate domain if validation on and idn_to_ascii is available.
	 * Rejects length greater than 255 or less than 5.
	 * Returns value of string tests or value of checkdnsrr.
	 *
	 * @since 1.0.0
	 * @param string $qm_address email address.
	 * @param string $validate_option Y or N.
	 * @return bool valid email address, or valid address and valid domain
	 */
	public static function qm_valid_email_domain( $qm_address, $validate_option = 'N' ) {
		$length = strlen( $qm_address );
		if ( 5 > $length || 255 < $length ) {
			return false;
		} // end if invalid length

		$a_split = explode( '@', trim( $qm_address ) );
		if ( ! is_array( $a_split ) || 2 !== count( $a_split ) || empty( $a_split[0] ) || empty( $a_split[1] ) ) {
			return false;
		} // return false if missing amphora

		if ( ! filter_var( $qm_address, FILTER_VALIDATE_EMAIL ) ) {
			return false;
		} // end if PHP rejects address

		if ( ! empty( $_SERVER['SERVER_ADDR'] ) ) {
			if ( ! self::acceptable_domain( $a_split[1] ) ) {
				return false;
			}
		} // does not work with WP-CLI

		if ( filter_var( $a_split[1], FILTER_VALIDATE_IP ) ) {
			return ( 'N' === $validate_option ) ? true : checkdnsrr( $a_split[1], 'MX' );
		} // end if IP address

		if ( ! strpos( $a_split[1], '.' ) ) {
			return false;
		} // end if no dots - localhost?

		if ( function_exists( 'idn_to_ascii' ) ) {
			$intl = defined( 'INTL_IDNA_VARIANT_UTS46' ) && defined( 'IDNA_NONTRANSITIONAL_TO_ASCII' ) ? idn_to_ascii( $a_split[1], IDNA_NONTRANSITIONAL_TO_ASCII, INTL_IDNA_VARIANT_UTS46 ) : idn_to_ascii( $a_split[1] );
			if ( ! empty( $intl ) ) {
				$a_split[1] = $intl;
			} // end if we have punycode address. xn--mrens-bsa.club = mérens.club.
		} // end if we have idn_to_ascii

		return ( 'N' === $validate_option ) ? true : checkdnsrr( $a_split[1], 'MX' );
	} // end qm_valid_email_domain

	/**
	 * Check if plugin is active.
	 *
	 * Does not require exact name like WordPress is_plugin_active().
	 *
	 * @param string $pname plugin name, or unique portion of name.
	 * @return boolean is this plugin active?
	 */
	public static function qm_is_plugin_active( $pname ) {
		$result       = false;
		$your_plugins = is_multisite() ?
		get_blog_option( get_current_blog_id(), 'active_plugins', array() ) :
		get_option( 'active_plugins', array() );

		if ( ! is_multisite() && ( ! is_array( $your_plugins ) || 1 > count( $your_plugins ) ) ) {
			return $result;
		} // end if not multisite and no plugins

		$all_plugins = array();
		if ( is_multisite() ) {
			$more_plugins = get_site_option( 'active_sitewide_plugins' );
			$all_plugins  = array_unique( array_merge( $your_plugins, array_keys( $more_plugins ) ) );
		} else {
			$all_plugins = $your_plugins;
		} // end if multisite
		foreach ( $all_plugins as $one ) {
			$result = stristr( $one, $pname );
			if ( is_string( $result ) ) {
				break;
			} // end if match
		} // end foreach

		return is_string( $result );
	} // end qm_is_plugin_active

	/**
	 * Get default sender name from WP.
	 *
	 * @param string $old_name for filter.
	 * @return string sender name
	 * @since 3.3.1
	 */
	public static function get_wp_user_name( $old_name = '' ) {
		$you  = wp_get_current_user();
		$name = '';
		if ( ! empty( $you->user_firstname ) && ! empty( $you->user_lastname ) ) {
			$name = "{$you->user_firstname} {$you->user_lastname}";
		} else {
			$name = $you->display_name;
		} // end if user has first and last names

		if ( empty( $name ) ) {
			$title     = __( 'Mail Error', 'quick-mail' );
			$desc      = __( 'Error: Incomplete User Profile', 'quick-mail' );
			$message   = "<a href='/wp-admin/profile.php'>{$desc}</a>";
			$direction = is_rtl() ? 'rtl' : 'ltr';
			$args      = array(
				'response'       => 200,
				'back_link'      => true,
				'text_direction' => $direction,
			);
			wp_die( sprintf( '<h1 role="alert">%s</h1>', esc_html( $title ), esc_html( $message ), $args ) );
		} // end if no name

		return $name;
	} // end get_wp_user_name

	/**
	 * Get default user email from WP.
	 *
	 * @param string $email arg for filter (not used).
	 * @return string email address
	 * @since 3.3.1
	 */
	public static function get_wp_user_email( $email = '' ) {
		$you = wp_get_current_user();
		if ( empty( $you->user_email ) ) {
			$title     = __( 'Mail Error', 'quick-mail' );
			$desc      = __( 'Error: Incomplete User Profile', 'quick-mail' );
			$message   = "<a href='/wp-admin/profile.php'>{$desc}</a>";
			$direction = is_rtl() ? 'rtl' : 'ltr';
			$args      = array(
				'response'       => 200,
				'back_link'      => true,
				'text_direction' => $direction,
			);
			wp_die( sprintf( '<h1 role="alert">%s</h1>', esc_html( $title ), esc_html( $message ), $args ) );
		} // end if no email

		return $you->user_email;
	} // end get_wp_user_name

	/**
	 * Do we have SparkPost plugin and credentials?
	 *
	 * @param boolean $check_from should we check if SparkPost name, email are set.
	 * @return boolean got SparkPost info
	 * @since 3.3.1
	 */
	public static function got_sparkpost_info( $check_from ) {
		if ( ! self::qm_is_plugin_active( 'sparkpost' ) ) {
			return false;
		} // end if not active

		if ( ! class_exists( 'WPSparkPost\SparkPost' ) ) {
			return false;
		} // end if cannot find class

		$active = WPSparkPost\SparkPost::get_setting( 'enable_sparkpost' );
		if ( empty( $active ) ) {
			return false;
		}

		$pw = WPSparkPost\SparkPost::get_setting( 'password' );
		if ( empty( $pw ) ) {
			return false;
		} // end if no password

		if ( false === $check_from ) {
			return true;
		} // end if checking install

		$from_name = WPSparkPost\SparkPost::get_setting( 'from_name' );
		$from_name = apply_filters( 'wpsp_sender_name', $from_name );

		$from_email = WPSparkPost\SparkPost::get_setting( 'from_email' );
		$from_email = apply_filters( 'wpsp_sender_email', $from_email );

		if ( empty( $from_email ) && empty( $from_name ) ) {
			return false;
		} // end if no name or email

		// We have name or email. Not validating email.
		return true;
	} // end got_sparkpost_info

	/**
	 * Get SparkPost credentials.
	 *
	 * @param array $wp_info 'name' => $name, 'email' => $email, 'reply_to' => $reply_to.
	 * @return string[] original or updated array
	 * @since 3.3.1
	 */
	public static function get_sparkpost_info( $wp_info ) {
		if ( ! self::got_sparkpost_info( true ) ) {
			return $wp_info;
		} // end if sparkpost is not active

		// SparkPost does not use definitions.
		$sp_email = WPSparkPost\SparkPost::get_setting( 'from_email' );
		if ( empty( $sp_email ) ) {
			$sp_email = apply_filters( 'wpsp_sender_email', $wp_info['email'] );
		} // end if
		$email = empty( $sp_email ) ? $wp_info['email'] : $sp_email;

		$sp_name = WPSparkPost\SparkPost::get_setting( 'from_name' );
		if ( empty( $sp_name ) ) {
			$sp_name = apply_filters( 'wpsp_sender_name', $wp_info['name'] );
		}
		$name     = empty( $sp_name ) ? $wp_info['name'] : $sp_name;
		$reply_to = apply_filters( 'wpsp_reply_to', $wp_info['reply_to'] );
		return array(
			'name'     => $name,
			'email'    => $email,
			'reply_to' => $reply_to,
		);
	} // end get_sparkpost_info

	/**
	 * Do we have Mailgun plugin and credentials?
	 *
	 * @param boolean $check_from should we check if Mailgun override-from is set.
	 * @return boolean got Mailgun info
	 * @since 3.2.0
	 */
	public static function got_mailgun_info( $check_from ) {
		if ( ! self::qm_is_plugin_active( 'mailgun' ) ) {
			return false;
		} // end if not active

		$options = array();
		if ( ! is_multisite() ) {
			$options = get_option( 'mailgun', array() );
		} else {
			$options = get_site_option( 'mailgun', array() );
			if ( empty( $options ) ) {
				$options = get_blog_option( get_current_blog_id(), 'mailgun', array() );
			} // end if no site option
		} // end if not multisite

		// from Mailgun plugin.
		$apikey = ( defined( 'MAILGUN_APIKEY' ) && MAILGUN_APIKEY ) ? MAILGUN_APIKEY : $options['apiKey'];
		$domain = ( defined( 'MAILGUN_DOMAIN' ) && MAILGUN_DOMAIN ) ? MAILGUN_DOMAIN : $options['domain'];
		if ( empty( $domain ) || empty( $apikey ) ) {
			return false;
		} // end if not using API or missing key / domain

		if ( false === $check_from ) {
			return true;
		} // end if not checking name, email

		if ( $check_from && empty( $options['override-from'] ) ) {
			return false;
		} // end if do not replace sender credentials

		return ! empty( $options['from-address'] );
	} // end got_mailgun_info

	/**
	 * Get Mailgun credentials.
	 *
	 * @param array $wp_info 'name' => $name, 'email' => $email, 'reply_to' => $reply_to.
	 * @return string[] original or updated array
	 * @since 3.2.0
	 */
	public static function get_mailgun_info( $wp_info ) {
		if ( ! self::qm_is_plugin_active( 'mailgun' ) ) {
			return $wp_info;
		} // end if Mailgun is not active

		$options = array();
		if ( ! is_multisite() ) {
			$options = get_option( 'mailgun', array() );
		} else {
			$options = get_site_option( 'mailgun', array() );
			if ( empty( $options ) ) {
				$options = get_blog_option( get_current_blog_id(), 'mailgun', array() );
			} // end if no site option
		} // end if not multisite

		if ( empty( $options['override-from'] ) || empty( $options['useAPI'] ) ) {
			return $wp_info;
		} // end if not using API or override from not set

		$apikey = ( defined( 'MAILGUN_APIKEY' ) && MAILGUN_APIKEY ) ? MAILGUN_APIKEY : $options['apiKey'];
		// From mailgun.php.
		$domain = ( defined( 'MAILGUN_DOMAIN' ) && MAILGUN_DOMAIN ) ? MAILGUN_DOMAIN : $options['domain'];
		if ( empty( $domain ) || empty( $apikey ) ) {
			return $wp_info;
		} // end if not using API or missing key / domain

		$email = $wp_info['email'];

		/*
		 *
		 * From Mailgun:
		 *  1. From address given by headers - {@param $from_addr_header}
		 *  2. From address set in Mailgun settings
		 *  3. From `MAILGUN_FROM_ADDRESS` constant
		 *  4. From address constructed as `wordpress@<your_site_domain>`
		 *  sender domain should match Mailgun domain
		*/

		$mg_email = '';
		if ( ! empty( $options['from-address'] ) ) {
			$mg_email = $options['from-address'];
		} elseif ( defined( 'MAILGUN_FROM_ADDRESS' ) ) {
			$mg_email = MAILGUN_FROM_ADDRESS;
		}

		if ( ! empty( $mg_email ) ) {
			if ( ! self::matches_email_domain( $email, $mg_email ) ) {
				$email = $mg_email;
			} // end if
		} // end if got Mailgun value

		$name = $wp_info['name'];
		if ( ! empty( $options['from-name'] ) ) {
			$name = $options['from-name'];
		} elseif ( defined( 'MAILGUN_FROM_NAME' ) ) {
			$name = MAILGUN_FROM_NAME;
		}  // end if have sender name

		// Mailgun plugin does not have reply-to setting.
		return array(
			'name'     => $name,
			'email'    => $email,
			'reply_to' => $wp_info['reply_to'],
		);
	} // end get_mailgun_info

	/**
	 * Is site using SendGrid? Check for active plugin with SendGrid in name.
	 *
	 * @param boolean $check_from default false. check if Sengrid from mail is set.
	 * @return boolean replace is active and optionally if config has an email address.
	 * @since 3.1.9
	 */
	public static function got_sendgrid_info( $check_from = false ) {
		if ( self::qm_is_plugin_active( 'mailgun' ) ) {
			return false;
		} // end if Mailgun is active. cannot use Sengrid with Mailgun.

		if ( class_exists( 'WPSparkPost\SparkPost' ) ) {
			$active = WPSparkPost\SparkPost::get_setting( 'enable_sparkpost' );
			if ( ! empty( $active ) ) {
				return false;
			} // end if SparkPost is active
		} // end if have SparkPost

		if ( ! self::qm_is_plugin_active( 'sendgrid' ) ) {
			return false;
		} // end if sendgrid is not active

		if ( false === $check_from ) {
			return true;
		} // end if not checking name, email

		// Check for SendGrid email.
		if ( defined( 'SENDGRID_FROM_EMAIL' ) && SENDGRID_FROM_EMAIL ) {
			return true;
		}
		$sg_email = '';
		if ( is_multisite() ) {
			$sg_email = get_site_option( 'sendgrid_from_email', '' );
			if ( empty( $sg_email ) ) {
				$sg_email = get_blog_option( get_current_blog_id(), 'sendgrid_from_email', 'N' );
			} // end if
		} else {
			$sg_email = get_option( 'sendgrid_from_email', '' );
		} // end if multisite

		return ! empty( $sg_email );
	} // end got_sendgrid_info

	/**
	 * Get SendGrid user info, if available.
	 *
	 * @param array $wp_info 'name' => $name, 'email' => $email.
	 * @return array updated array
	 * @since 3.1.9
	 */
	public static function get_sendgrid_info( $wp_info ) {
		if ( ! self::got_sendgrid_info() ) {
			return $wp_info;
		}

		// Sendgrid_Tools::get_from_name, get_from_email, get_reply_to test for define first.
		$sg_name     = defined( 'SENDGRID_FROM_NAME' ) ? SENDGRID_FROM_NAME : '';
		$sg_email    = defined( 'SENDGRID_FROM_EMAIL' ) ? SENDGRID_FROM_EMAIL : '';
		$sg_reply_to = defined( 'SENDGRID_REPLY_TO' ) ? SENDGRID_REPLY_TO : '';

		if ( is_multisite() ) {
			$sg_name  = empty( $sg_name ) ? get_site_option( 'sendgrid_from_name', '' ) : get_blog_option( get_current_blog_id(), 'sendgrid_from_name', '' );
			$sg_email = empty( $sg_email ) ? get_site_option( 'sendgrid_from_email', '' ) : get_blog_option( get_current_blog_id(), 'sendgrid_from_email', '' );
		} else {
			if ( empty( $sg_name ) ) {
				$sg_name = get_option( 'sendgrid_from_name' );
			}
			if ( empty( $sg_email ) ) {
				$sg_email = get_option( 'sendgrid_from_email' );
			}
		} // end if multisite

		$email    = empty( $sg_email ) ? $wp_info['email'] : $sg_email;
		$name     = empty( $sg_name ) ? $wp_info['name'] : $sg_name;
		$reply_to = '';
		if ( ! empty( $sg_reply_to ) ) {
			$reply_to = $sg_reply_to;
		} elseif ( empty( $wp_info['reply_to'] ) ) {
			$reply_to = $wp_info['reply_to'];
		} else {
			$reply_to = $email;
		} // end if

		return array(
			'name'     => $name,
			'email'    => $email,
			'reply_to' => $reply_to,
		);
	} // end get_sendgrid_info


	/**
	 * Is user using the same domain as SparkPost?
	 *
	 * @return boolean if user and SparkPost are using the same domain.
	 * @since 3.3.3
	 */
	public static function using_sparkpost_domain() {
		$wp_domain    = '';
		$spark_domain = '';
		$wpmail       = self::get_wp_user_email();
		$sparkmail    = WPSparkPost\SparkPost::get_setting( 'from_email' );
		$qsplit       = explode( '@', $sparkmail );
		if ( is_array( $qsplit ) && ! empty( $qsplit[1] ) ) {
			$spark_domain = $qsplit[1];
		} // end if

		$qsplit = explode( '@', $wpmail );
		if ( is_array( $qsplit ) && ! empty( $qsplit[1] ) ) {
			$wp_domain = $qsplit[1];
		} // end if

		return ( ! empty( $spark_domain ) && $spark_domain === $wp_domain );
	} // end using sparkpost domain

	/**
	 * Should SparkPost transaction be toggled for attachments?
	 *
	 * @param array $attachments user's attachments.
	 * @since 3.3.1
	 */
	public static function toggle_sparkpost_transactional( $attachments ) {
		$retval = false;
		$trans  = WPSparkPost\SparkPost::get_setting( 'transactional' );
		if ( ! empty( $trans ) && is_array( $attachments ) && ! empty( $attachments ) ) {
			$retval = true;
			add_filter( 'wpsp_transactional', '__return_zero', 2017, 0 );
		} // end if
		return $retval;
	} // end toggle_sparkpost_transactional

	/**
	 * Get email domain to check for matching service sender domain.
	 *
	 * @param string $email email address.
	 * @return string domain or empty if missing amphora.
	 * @since 3.3.5
	 */
	public static function get_email_domain( $email ) {
		$a_split = explode( '@', trim( $email ) );
		if ( ! is_array( $a_split ) || 2 !== count( $a_split ) || empty( $a_split[0] ) || empty( $a_split[1] ) ) {
			return '';
		} // return false if missing amphora

		return $a_split[1];
	} // end get_email_domain

	/**
	 * Check if both email addresses use the same top level domain.
	 *
	 * @param string $e1 email 1.
	 * @param string $e2 email 2.
	 * @return boolean do addresses use the same domain?
	 */
	public static function matches_email_domain( $e1, $e2 ) {
		$d1     = self::get_email_domain( $e1 );
		$d2     = self::get_email_domain( $e2 );
		$len1   = strlen( $d1 );
		$len2   = strlen( $d2 );
		$result = ( $len1 > $len2 ) ? strstr( $d1, $d2 ) : strstr( $d2, $d1 );
		return is_string( $result );
	} // end matches_email_domain

	/**
	 * Does this user have comments?
	 *
	 * @param integer $id User ID.
	 * @return boolean if user has any comments.
	 * @since 3.5.0
	 */
	public static function user_has_comments( $id ) {
		$args   = array(
			'post_author' => $id,
			'post_status' => 'publish',
			'status'      => 'approve',
			'count'       => true,
		);
		$cquery = get_comments( $args );
		return ( 0 < $cquery );
	} // end user_has_comments

	/**
	 * Count recipients in email headers.
	 *
	 * @param array $headers Email headers.
	 * @return integer count of recipients
	 * @since 3.5.2
	 */
	public static function count_recipients( $headers ) {
		$recipients = 2; // To and From.
		foreach ( $headers as $one ) {
			$got = count_chars( $one, 1 );
			if ( ! empty( $got ) && ! empty( $got[64] ) ) {
				$recipients += $got[64];
			} // Add amphora count.
		} // end foreach.
		return $recipients;
	} // end count_recipients

} // end class