Several, though none can be fairly called "letters." [ She blows on her nails again ]

I'm trying to work out where they receive ours from - Ushiromiya confirmed to me that it is possible somehow.

[ Which is probably too practical and she knows it. If she were as sentimental as some others, she might've written them even knowing they wouldn't be received. But... She isn't like that. Or at last tells herself she isn't ]