This is excellent and greatly-timed for me. Recently I acquainted with a mentor of sorts online. After some back-and-forth through email we decided to try our hand at sending letters via old-fashioned mail.
The result is much more personal, but more than that: writing a letter by hand elicits a deeper type of messaging, where thoughts aren't merely typed out quickly. In addition to the deeper and more in-depth letters, the mail allows us to send physical items back-and-forth as well, including photos of our work and other, small mementoes that are more valuable than digital goods simply because of their tangible presence.