Letter storage

I am currently out of letters to reply to, and none came today (no post whatsoever for me, although I did feed a postbox with 10 postcards for Postcrossing). Anyway, I thought I would blog about letter storage. 

Currently, I store letters in little A5 zip folders, one for each penpal, but the folders for some penpals are getting rather fat! Perhaps I'll just use a second folder for those penpals.... I keep the letters, where possible, in their original envelopes, and number them with a little circle sticker. One penpal, I have replied to her 50th letter!

Is there a better way to store letters? Plastic doesn't seem all that romantic, and I would prefer a nicer way to store the letters. Perhaps I will scan them in at some point, to have a digital copy available...