For Red Hat Enterprise Linux 5, what is a good secure FTP solution that will integrate with e-mail and avoid having the customer use a third-party client to authenticate to upload and download files through a chroot jail? The ideal solution would be to have a secure web-based interface that I could easily integrate into an existing site without alot of hassle, where the secure session is initiated through an e-mail sent to the client. However, I'm finding mostly expensive convoluted enterprise solutions or low-end anonymous FTP daemons. Each customer is unique, and I don't want to simply have a file dump for everyone to see. Yes, I have tried WebDAV on the Microsoft end, but even that seems too complicated for some people, any suggestions?