@GauthierCurrently, all archival files - EPUB, .mobi, TXT and Zip - are saved on the server using the story's ID number. When downloaded, the files are renamed on the fly according to the user's preference.
It's basically always been like this, but previously, when I emailed .mobi files, the kindle got the file name from the file's meta data.
It seems something changed in Amazon's conversion process and now they're ignoring the EPUB's built in meta data.
So even if I rename the file before attaching to the email message, the author would still be unknown.
It will take some work, but I'll attach the file with proper file name.