Yes. Dept. of Post website is down and the other link is not available right now.
Try this link here. for the list of Public Authorities covered by the Postal Dept.
Otherwise all these files are available with me and I can share the same with you if you are interested.
p.s. I am also getting error messages in RTIindia.org site. Lots of mySQL errors at the top of the page and the site is loading slowly. Perhaps the admins are doing some backend jobs.