Sending data from one machine to another

I would like to send data from one laptop to another via the internet.

I'd like to be able to send the data to multiple machines that may not be currently connected to the internet, but they should recieve it when they are connected.

I have webspace with FTP access, and think it might be possible to upload the data to the server with tags so that a script can search the directory, find the data, then get it. Is this possible?

I also thought about an email type client, as I have unlimited email accounts on the same webspace, I could then set up an email account for each user, but present it more like a Instant messenger type app. Is this possible?

Or is none of this possible? or should I be doing anything else.
The data is mostly text strings, like emails, but in a defined format.

Thanks in advance :-)