//.........这里部分代码省略.........
                        // Can't find group
                        continue;
                        // Be safe and don't send it to anyone
                    }
                    if (!groups_is_member($discussion->groupid) and !has_capability('moodle/site:accessallgroups', $modcontext)) {
                        // do not send posts from other groups when in SEPARATEGROUPS or VISIBLEGROUPS
                        continue;
                    }
                }
                // Make sure we're allowed to see it...
                if (!forum_user_can_see_post($forum, $discussion, $post, NULL, $cm)) {
                    mtrace('user ' . $userto->id . ' can not see ' . $post->id);
                    continue;
                }
                // OK so we need to send the email.
                // Does the user want this post in a digest?  If so postpone it for now.
                if ($userto->maildigest > 0) {
                    // This user wants the mails to be in digest form
                    $queue = new object();
                    $queue->userid = $userto->id;
                    $queue->discussionid = $discussion->id;
                    $queue->postid = $post->id;
                    $queue->timemodified = $post->created;
                    if (!insert_record('forum_queue', $queue)) {
                        mtrace("Error: mod/forum/cron.php: Could not queue for digest mail for id {$post->id} to user {$userto->id} ({$userto->email}) .. not trying again.");
                    }
                    continue;
                }
                // Prepare to actually send the post now, and build up the content
                $cleanforumname = str_replace('"', "'", strip_tags(format_string($forum->name)));
                $userfrom->customheaders = array('Precedence: Bulk', 'List-Id: "' . $cleanforumname . '" <moodleforum' . $forum->id . '@' . $hostname . '>', 'List-Help: ' . $CFG->wwwroot . '/mod/forum/view.php?f=' . $forum->id, 'Message-ID: <moodlepost' . $post->id . '@' . $hostname . '>', 'In-Reply-To: <moodlepost' . $post->parent . '@' . $hostname . '>', 'References: <moodlepost' . $post->parent . '@' . $hostname . '>', 'X-Course-Id: ' . $course->id, 'X-Course-Name: ' . format_string($course->fullname, true));
                $postsubject = "{$course->shortname}: " . format_string($post->subject, true);
                $posttext = forum_make_mail_text($course, $forum, $discussion, $post, $userfrom, $userto);
                $posthtml = forum_make_mail_html($course, $forum, $discussion, $post, $userfrom, $userto);
                // Send the post now!
                mtrace('Sending ', '');
                if (!($mailresult = email_to_user($userto, $userfrom, $postsubject, $posttext, $posthtml, '', '', $CFG->forum_replytouser))) {
                    mtrace("Error: mod/forum/cron.php: Could not send out mail for id {$post->id} to user {$userto->id}" . " ({$userto->email}) .. not trying again.");
                    add_to_log($course->id, 'forum', 'mail error', "discuss.php?d={$discussion->id}#p{$post->id}", substr(format_string($post->subject, true), 0, 30), $cm->id, $userto->id);
                    $errorcount[$post->id]++;
                } else {
                    if ($mailresult === 'emailstop') {
                        // should not be reached anymore - see check above
                    } else {
                        $mailcount[$post->id]++;
                        // Mark post as read if forum_usermarksread is set off
                        if (!$CFG->forum_usermarksread) {
                            $userto->markposts[$post->id] = $post->id;
                        }
                    }
                }
                mtrace('post ' . $post->id . ': ' . $post->subject);
            }
            // mark processed posts as read
            forum_tp_mark_posts_read($userto, $userto->markposts);
        }
    }
    if ($posts) {
        foreach ($posts as $post) {
            mtrace($mailcount[$post->id] . " users were sent post {$post->id}, '{$post->subject}'");
            if ($errorcount[$post->id]) {
                set_field("forum_posts", "mailed", "2", "id", "{$post->id}");
            }
        }
    }
    // release some memory

//.........这里部分代码省略.........
                    // This user wants the mails to be in digest form
                    $queue = new stdClass();
                    $queue->userid       = $userto->id;
                    $queue->discussionid = $discussion->id;
                    $queue->postid       = $post->id;
                    $queue->timemodified = $post->created;
                    $DB->insert_record('forum_queue', $queue);
                    continue;
                }


                // Prepare to actually send the post now, and build up the content

                $cleanforumname = str_replace('"', "'", strip_tags(format_string($forum->name)));

                $userfrom->customheaders = array (  // Headers to make emails easier to track
                           'Precedence: Bulk',
                           'List-Id: "'.$cleanforumname.'" <moodleforum'.$forum->id.'@'.$hostname.'>',
                           'List-Help: '.$CFG->wwwroot.'/mod/forum/view.php?f='.$forum->id,
                           'Message-ID: '.forum_get_email_message_id($post->id, $userto->id, $hostname),
                           'X-Course-Id: '.$course->id,
                           'X-Course-Name: '.format_string($course->fullname, true)
                );

                if ($post->parent) {  // This post is a reply, so add headers for threading (see MDL-22551)
                    $userfrom->customheaders[] = 'In-Reply-To: '.forum_get_email_message_id($post->parent, $userto->id, $hostname);
                    $userfrom->customheaders[] = 'References: '.forum_get_email_message_id($post->parent, $userto->id, $hostname);
                }

                $shortname = format_string($course->shortname, true, array('context' => context_course::instance($course->id)));

                $postsubject = html_to_text("$shortname: ".format_string($post->subject, true));
                $posttext = forum_make_mail_text($course, $cm, $forum, $discussion, $post, $userfrom, $userto);
                $posthtml = forum_make_mail_html($course, $cm, $forum, $discussion, $post, $userfrom, $userto);

                // Send the post now!

                mtrace('Sending ', '');

                $eventdata = new stdClass();
                $eventdata->component        = 'mod_forum';
                $eventdata->name             = 'posts';
                $eventdata->userfrom         = $userfrom;
                $eventdata->userto           = $userto;
                $eventdata->subject          = $postsubject;
                $eventdata->fullmessage      = $posttext;
                $eventdata->fullmessageformat = FORMAT_PLAIN;
                $eventdata->fullmessagehtml  = $posthtml;
                $eventdata->notification = 1;

                // If forum_replytouser is not set then send mail using the noreplyaddress.
                if (empty($CFG->forum_replytouser)) {
                    // Clone userfrom as it is referenced by $users.
                    $cloneduserfrom = clone($userfrom);
                    $cloneduserfrom->email = $CFG->noreplyaddress;
                    $eventdata->userfrom = $cloneduserfrom;
                }

                $smallmessagestrings = new stdClass();
                $smallmessagestrings->user = fullname($userfrom);
                $smallmessagestrings->forumname = "$shortname: ".format_string($forum->name,true).": ".$discussion->name;
                $smallmessagestrings->message = $post->message;
                //make sure strings are in message recipients language
                $eventdata->smallmessage = get_string_manager()->get_string('smallmessage', 'forum', $smallmessagestrings, $userto->lang);

                $eventdata->contexturl = "{$CFG->wwwroot}/mod/forum/discuss.php?d={$discussion->id}#p{$post->id}";

//.........这里部分代码省略.........
                // OK so we need to send the email.
                // Does the user want this post in a digest?  If so postpone it for now.
                $maildigest = forum_get_user_maildigest_bulk($digests, $userto, $forum->id);
                if ($maildigest > 0) {
                    // This user wants the mails to be in digest form.
                    $queue = new stdClass();
                    $queue->userid = $userto->id;
                    $queue->discussionid = $discussion->id;
                    $queue->postid = $post->id;
                    $queue->timemodified = $post->created;
                    $DB->insert_record('forum_queue', $queue);
                    continue;
                }
                // Prepare to actually send the post now, and build up the content.
                $cleanforumname = str_replace('"', "'", strip_tags(format_string($forum->name)));
                $userfrom->customheaders = array('List-Id: "' . $cleanforumname . '" <moodleforum' . $forum->id . '@' . $hostname . '>', 'List-Help: ' . $CFG->wwwroot . '/mod/forum/view.php?f=' . $forum->id, 'Message-ID: ' . forum_get_email_message_id($post->id, $userto->id, $hostname), 'X-Course-Id: ' . $course->id, 'X-Course-Name: ' . format_string($course->fullname, true), 'Precedence: Bulk', 'X-Auto-Response-Suppress: All', 'Auto-Submitted: auto-generated');
                $shortname = format_string($course->shortname, true, array('context' => context_course::instance($course->id)));
                // Generate a reply-to address from using the Inbound Message handler.
                $replyaddress = null;
                if ($userto->canpost[$discussion->id] && array_key_exists($post->id, $messageinboundhandlers)) {
                    $messageinboundgenerator->set_data($post->id, $messageinboundhandlers[$post->id]);
                    $replyaddress = $messageinboundgenerator->generate($userto->id);
                }
                if (!empty($CFG->forum_enabletimedposts) && $discussion->timestart > $post->modified) {
                    // Override the post->modified time with the discussion start for e-mails.
                    $post->modified = $discussion->timestart;
                }
                $a = new stdClass();
                $a->courseshortname = $shortname;
                $a->forumname = $cleanforumname;
                $a->subject = format_string($post->subject, true);
                $postsubject = html_to_text(get_string('postmailsubject', 'forum', $a), 0);
                $posttext = forum_make_mail_text($course, $cm, $forum, $discussion, $post, $userfrom, $userto, false, $replyaddress);
                $posthtml = forum_make_mail_html($course, $cm, $forum, $discussion, $post, $userfrom, $userto, $replyaddress);
                $rootid = forum_get_email_message_id($discussion->firstpost, $userto->id, $hostname);
                if ($post->parent) {
                    // This post is a reply, so add reply header (RFC 2822).
                    $parentid = forum_get_email_message_id($post->parent, $userto->id, $hostname);
                    $userfrom->customheaders[] = "In-Reply-To: {$parentid}";
                    // If the post is deeply nested we also reference the parent message id and
                    // the root message id (if different) to aid threading when parts of the email
                    // conversation have been deleted (RFC1036).
                    if ($post->parent != $discussion->firstpost) {
                        $userfrom->customheaders[] = "References: {$rootid} {$parentid}";
                    } else {
                        $userfrom->customheaders[] = "References: {$parentid}";
                    }
                }
                // MS Outlook / Office uses poorly documented and non standard headers, including
                // Thread-Topic which overrides the Subject and shouldn't contain Re: or Fwd: etc.
                $a->subject = $discussion->name;
                $postsubject = html_to_text(get_string('postmailsubject', 'forum', $a), 0);
                $userfrom->customheaders[] = "Thread-Topic: {$postsubject}";
                $userfrom->customheaders[] = "Thread-Index: " . substr($rootid, 1, 28);
                // Send the post now!
                mtrace('Sending ', '');
                $eventdata = new \core\message\message();
                $eventdata->component = 'mod_forum';
                $eventdata->name = 'posts';
                $eventdata->userfrom = $userfrom;
                $eventdata->userto = $userto;
                $eventdata->subject = $postsubject;
                $eventdata->fullmessage = $posttext;
                $eventdata->fullmessageformat = FORMAT_PLAIN;
                $eventdata->fullmessagehtml = $posthtml;
                $eventdata->notification = 1;