I have just finished to create a "mendelson" AS2Box that sends *.txt messages to the mendelson AS2 test server.
You can connect to the "mendelson" AS2Box via FTP:
Then, you just "put" a *.txt and it will be sent to the mendelson AS2 test server. You can then check that your file is well arrived on the mendelson AS2 test server by pointing your browser to http://as2.mendelson-e-c.com:8080/webas2 with user: guest and password: guest.
The MDN will be copied in /outgoing/archive.
Do not hesitate to contact me if you would have any further questions...