如何根据用户创建的标签获取电子邮件

how to specify user created label in imap_open my label name is lead

  $mailbox = imap_open("{imap.googlemail.com:993/ssl}lead", "USERNAME@googlemail.com", "PASSWORD");
        $mail = imap_search($mailbox, "ALL");
        $mail_headers = imap_headerinfo($mailbox, $mail[0]);
        $subject = $mail_headers->subject;
        $from = $mail_headers->fromaddress;
        imap_setflag_full($mailbox, $mail[0], "\\Seen \\Flagged");
        imap_close($mailbox);

but i didn't get any mails