Actually the Vikram said he had initially added a search feature and it didn't appear to be very useful. He says:

   search is an awful way to curate text when your readers don't know what is interesting about it. This is obvious in retrospect, but it didn't occur to me until I showed what I built to folks.

Though there are at least 41 different tags that he applied to the threads and can be found here: https://atariemailarchive.org/categories

He talks about this in his post: https://vikramoberoi.com/how-i-made-atariemailarchive-org/

I originally heard about this on the Data Is Plural podcast: https://podcast.data-is-plural.com/2159594/12535597