Over the years I've had pen pals. We've always started off strong, letters back and forth frequently but as time passes there is more and more gaps in between letters until finally it just stops. Recently I started using Postcrossing, which is a site that allows people to send and receive postcards from around the world. I enjoy writing letters and mailing them off so a blog post called Anatomy of a Regency Letter certainly caught my attention.
This post discusses things like the paper used
and the format of writing the letter.
It also shows you how to properly fold a letter for mailing.