This document summarizes a presentation about building a network of open correspondence projects. It discusses why a network is needed, as letters create graphs between people and places like the web. It advocates for open science principles where primary sources, transcriptions, metadata and other materials are digital, online, open and linked. Examples are given of existing open science projects in different domains. The presentation argues that open science allows for "planned serendipity" and changes the direction of knowledge sharing for the benefit of the scholarly community.