I see that on Mon, Jun 30, 2008 2:49 pm, JeniferC was considering,

putting files on another outside server,

but,

because of security issues around making sure the files
... can only be downloaded by the people that have bought them

That is trivial to accomplish ...

On that temporary server, you upload the zip files into folders named renderosity/key[n]/
where key[n] is a different 8-digit random number for each scheduled recipient ... send
those keys by eMail to each user individually ... ask that they download promptly and say when that has been successful ... delete that buyer's zip file(s). 

Any questions???

--
Martin