Notes: Individual entries let you track incoming and outgoing.
I have one place on the main screen for inserting a scanned image of the letter. I will have a place for a letter per note entry when done. The "where did I get this pan-pal from" is editable and adds the entry for future use. And yes I know I got the site wrong for good mail day. Already fixed.
Like I said, this is basically an open source database. You give a good suggestion and I will see if it makes sense to add it.