Backing up a server over the internet

I have some customers that do not have backup drives on their servers. They want to use one of my servers to do a nightly backup. Is this a job for IIS5.0 FTP Server. Also, if my clients network crash and they repair it and I have to send data back to them. Will they have to go through the steps of converting the data from ASCII back to it’s original format?
I’m open to suggestions or is there a better software I can purchase that will do it better.