There is not enough disk space to download new messages. Try deleting old mail, emptying the Trash folder, and compacting your mail folders, and then try again.
没有足够的磁盘空间用来下载新消息。请尝试删除旧邮件、清空“废件箱”文件夹、压缩您的邮件文件夹，然后再试。