Yes, you can file RTI to India Post to get information regarding your consignment. The Department of Posts (DoP), trading as India Post, is a government-operated postal system in India under the Department of Posts, which is part of the Ministry of Communications of the Government of India.
Since it is a government-operated postal system. Therefore, it comes under the ambit of section 2(h) of the RTI Act'2005 which has the definition of Public Authority. Hence, we can file RTI to India Post.
For further assistance and to have a better understanding on filing RTI, you may visit the below mentioned link:
https://onlinerti.com/how-to-file-rti-online-for-center