Dear Sir,
here's how I'd do it:
* Set up a "normal" email account. It doesn't matter where, it can your hoster, a freemail service, or anything, as long as it supports pop3.
* I will then use python's poplib to query that account for any incoming email and get its attachment
* Python's ftplib will then do the upload to your ftp server.
* We then run the tool automatically every x minutes, frequency can be tuned to the amount of incoming email.
You get:
* The python command line tool with built-in documentation
* It's documented source code
* Assistance to set up the program on your machine. If you can give me SSH access, I can also do this for you.
Requirements on your site: A machine that can run python and execute timed jobs. That's every linux or windows machine, unless your access is restricted. Webservers with shell access are the best option.
Feel free to contact me with any questions.
Best Regards
Sebastian Schmied