hi there

you can look at hotmail for an example user interface. As for the code itself, the servlet should save the file(s) locally using the jsessionid or some other unique id to associate it to the user (the servlet API has a method for allocating temporary files), then you gather the rest of the data and generate the message.
As for sending an email with attachment, you can look at this page which has a nice example, as well as multiple links to other sources of information. You also browse through the FAQ here on jguru. John Zukowski is doing a great job maintaining it.

cheers