PMFJI but Randy Brown gave a session at Dev-Con thats sounds like it could handle some of the things your talking about. I have not used it nor do i know for sure that its a good fit, but it may save you from reinventing the wheel.
I think MS Message Queue and FoxPro com servers or something Like that was the name. My understanding was you can use this to have messages and or file sent to anyone and have verification they recieved.

Might be worth a look.

HTH
Jeff

>>My client has asked me to do a feasibility study on transferring files between 2 PC via the internet.
>>
>>I would like your input on:
>>- What is the best method to transfer files? (E-mail, FTP, etc.)
>>- What tool is best suited for this task? (ActiveX from MS, 3-party tool, etc.)
>>- When one PC receive a file, it may have some file to send to the sender. How it can be implemented?
>>- How an application can retreive the files when it's received?
>>- Hardware consideration?
>>- This fonctionality must be implemented as a COM to be integrated in other applications. Any gotchas?
>>
>>TIA
>
> We have plans to implement this for 1100 clients, and it is becoming a major headache. Our decision was to implement FTP through a technology known as Remote Lan Dial from MCI. Our clients connect to this like an ISP through DUN, and are attached to our LAN.
>
> The clients we have with large network infrastructures are causing the majority of the problems. If you attempt to connect to an IP through the RLD connection, it will not route the correct way - it tries to go through the IP structure of the LAN, and not through the internet connection. From what we have discovered, this still may be the case when we move from MCI to the internet.
>
> Another option we are investigating is the use of e-mail. This may end up being our best solution, but because there is no direct connection to our network, we will have to implement e-mail verification (return receipts) to ensure the files are received here and at the clients.
>
> In a nutshell, it's just not simple or easy to implement. Good luck though!!!
>
>Wayne