I have a recipe to send files from a dropbox folder to my @kinde email address to be converted and delivered to my device. The problem is… the filename ends up "mangled". Say I copy a file, "Pacific Express.pdf", into the folder. It ends up on my kindle as "pacific20express".
File naming is very important on the Kindle. It takes the name of the file without the extension as the display-name for the book on the device. It cannot be renamed on the device or the online content manager. This makes for a very ugly library and effectively ruins the recipe.
I suspect that IFTTT is downcasing and URL-encoding the FileUrl component (of the recipe) and that Kindle is stripping the % from the URL-encoded space, %20.
I don't know if this can be fixed or worked-around. When I manually attach/email these files to my @kindle email address it shows up with the casing/punctuation preserved.
Best Answer
Previously, I have used wappwolf (an alternative app) to solve this, but it closed down in the last couple of days. https://twitter.com/WAPPWOLF/status/983629320697491457
I discovered a new solution today, using "Microsoft Flow" (which I had never heard of before). https://flow.microsoft.com
When I automate a Dropbox to email/Google Drive using its service, the Filename and extension are retained. Give that a go. That might work for you until IFTTT adjust their protocol.