Any Official Source to Get Postal Codes of Spain?

Hi Everyone!

I am programming a web portal for my Spanish friend, and now I need to include a dataset of Spanish postal codes. I was about to fetch it from Google developer's tool, but according to my friend, it should be more updated, and at least it should be published by any government or official Spanish site. I would be grateful if you share any of these sites with me.

By the way, I also found this site a good source to fetch Spanish postal codes among the postal codes of other countries, and it also supports my framework. But, I am not sure how much dataset is accurate at GeoNames, especially when it comes to Spanish postal codes and geo-related information. I would be thankful if you give your suggestion about the accuracy of postal codes available on GeoNames because this Back4App site is extracting data from there. Moreover, you can also share any official site because my first preference would be any government site.

Please come with your suggestions, especially if you are a programmer then it would be great.