Hi all,
I saw that Bhuvan has a portal for Post offices, and I decided to poke around a bit, and I found that the data could be Scraped.
I have scrapped the data from this portal for all the pincodes, which in turn are available on the
data.gov.in website.
While this data does not cover the entire country (Quite a few gaps are visible), It's a good start, and gives locations for post-offices in quite a large fraction of the country.
This data also contains the attributes for pincodes, so it will also serve the need for an half decent pincode location dataset.
This data is available at the following Google drive location: