使用PHP IMAP连接到交换服务器，交换服务器对未见过的邮件使用什么标志?

我使用的是封装在Barbushin的方便小类中的PHP IMAP库:https://github.com/barbushin/php-imap

我开始测试我的gmail帐户，它会收到以下内容的未读邮件。

$imap = new IMAP();
$unseen = $imap->searchMailbox('UNSEEN');

类中的函数执行以下操作:

/*
 *      ALL - return all mails matching the rest of the criteria
 *      ANSWERED - match mails with the ''ANSWERED flag set
 *      BCC "string" - match mails with "string" in the Bcc: field
 *      BEFORE "date" - match mails with Date: before "date"
 *      BODY "string" - match mails with "string" in the body of the mail
 *      CC "string" - match mails with "string" in the Cc: field
 *      DELETED - match deleted mails
 *      FLAGGED - match mails with the ''FLAGGED (sometimes referred to as Important or Urgent) flag set
 *      FROM "string" - match mails with "string" in the From: field
 *      KEYWORD "string" - match mails with "string" as a keyword
 *      NEW - match new mails
 *      OLD - match old mails
 *      ON "date" - match mails with Date: matching "date"
 *      RECENT - match mails with the ''RECENT flag set
 *      SEEN - match mails that have been read (the ''SEEN flag is set)
 *      SINCE "date" - match mails with Date: after "date"
 *      SUBJECT "string" - match mails with "string" in the Subject:
 *      TEXT "string" - match mails with text "string"
 *      TO "string" - match mails with "string" in the To:
 *      UNANSWERED - match mails that have not been answered
 *      UNDELETED - match mails that are not deleted
 *      UNFLAGGED - match mails that are not flagged
 *      UNKEYWORD "string" - match mails that do not have the keyword "string"
 *      UNSEEN - match mails which have not been read yet
 *
 * @return array Mails ids
 */
public function searchMailbox($criteria = 'ALL') {
    $mailsIds = imap_search($this->imapStream, $criteria, SE_UID, $this->serverEncoding);
    return $mailsIds ? $mailsIds : array();
}

只是imap_search();的一个方便的包装http://php.net/manual/en/function.imap-search.php

通过IMAP成功连接到我的交换服务器，现在我可以做以下操作:

$imap = new IMAP();
$unseen = $imap->searchMailbox('ALL');

这将检索Exchange上收件箱中的所有电子邮件(根据我的连接)。

UNSEEN(如文档所示)在Google Mail上按预期工作，但在Exchange 2010上不行。ALL在两者上都按预期工作。我想知道Exchange 2010是否使用了不同的标志?NEW和UNREAD也不工作。并且我可以从这些mailID中获得的返回的详细信息不包含要从中进行逆向工程的标志数组。

任何帮助都将非常感谢:)