I wish I could be bothered to save mine, but I toss almost every one away. I have 5 special ones in my letters slot in my pockets, I switch them out from time to time. I don't really like getting mail from 'mom', I find it a bit weird personally, so I chuck all hers away

sorry Mom!
- - - Post Merge - - -
If you go to the post office and talk to Pelly, choose 'Save Letter' and you can drag letters from your pockets into a save box and store them there. You can also attach items to the letters too and use it for extra storage space ^^