Security is not a concern for the purpose of my question here, please ignore that for now. I'm just looking for text summary and search functionality here, not looking to give it full system access and let it loose on my computer or network. I can easily set up VM/sandboxing/airgapping/etc. as needed.

My question is really just about what can handle that volume of data (ideally, with the quoted sections/duplications/etc. that come with email chains) and still produce useful (textual) output.