Can anyone suggest a reliable and inexpensive (possibly open-source) method of delivering files automatically over the internet. Primarily, and as an example, I am looking to deliver free a mp3 file (possibly compressed to zip) to those customers who have just registered their details with my mailing list. This means that they will not have passed through a checkout. I would also need to ensure the download link for their delivery is secure, and only allows for the download to be accessed to a maximum of perhaps 5 times before expiry. The delivery system must be installed on my own web hosts server. I have seen some programs that look like they will do what I am looking for, but they are (in my opinion) either quite expensive (when you take into consideration that I am giving files away free and am not likely to recover any money), or operate through a third-party. Suggestions gratefully received.