Hello

Ok so heres the rundown. I just got a job as a webmaster, first order of buisness is to start a mailing list. All I have to work with for a few months is php. (mySQL won't come around till later for reasons i have yet to find out)

So heres the deal, I don't have my code finalized yet, and it's at work. But here is the concept-

Enter a bunch of address info on form->
write to CSV excel file...

simple enough right?

What I'm worried about, is for this to work, the permissions need to be set to writable. I need some hints on how I can secure this document so nobody can do any kind of injection, flooding, or retrieve it and use the addresses to spam. I am the only one that needs to see this file, so setting the permissions for only my access is A-ok. but of course then nobody could write to it. Basically, I just need some pep talk and advice because this is the first time I am doing this for someone else. How can I make sure this doesn't get screwed up?