Few space is not set to Public so new trackbacks can not be created. But the Permalink is available to the friends, so if you want to trackback, just change ".entry" of the permalink to ".trak", and then trackback function will work! However, if the author disable this trackback function, then nothing can be done.
Reproduced in: https: //www.cnblogs.com/civ3/archive/2006/02/16/332118.html