If you decided to move from tumblr blog / pages from your top level domain to a subdomain like blog.example.in .
Add the entry in your .htaccess to allow Apache send all requests from /post to the new subdomain which Tumblr is right now hosting (blog.example.in).
Redirect 301 /post http://blog.example.in/post
301 Redirect is a permanent move. Ideally, the same client would not query the same post again at the same url.
Sairam's Blog 