What are great examples of comprehensively archived mathematical correspondence (including both handwritten and electronic items)?
Context: polished papers usually don't reveal the full process that accompanied the way definitions and proofs wherewere conceived. For example, Colmez's introduction to the book Courbes et fibrés vectoriels en théorie de Hodge p-adique by Fargues and Fontaine, contains long excerpts of email exchanges which are very interesting.