I have a problem with a kinda rare software. It is called Sitatex and it is a simple messaging software, used in air transport companies. It works in conjunction with a special modem, that has a dedicated connection(leased line) to Sitatex servers. It noes not work with Internet. The companies use it for secure message send/receive regarding cargo(at least as far as I am concerned). The messages are really simple. The user must type the recipient's address, a subject, the message(a text message that follows certain patterns), and then sends the message. Also, the message can have attached files. Kinda similar to e-mails. Sitatex works in a server - client mode. The client is installed on the workstations, communicates with the server via LAN. The server then sends the messages actually to the system, using a server software, the modem and the leased line.
Now, what I need to do is to send messages automatically in this Sitatex system. I have a software that composes messages. All I need now is to send them. And here I am stuck.
The version of Sitatex I am working with is Sitatex 3. On the web sites I find that what I need to do can be done using Sitatex SDK (that's the name of their API). I cannot get this as I don't find it anywhere for the version of Sitatex I am using. So I am looking for a way to go around this problem.
One approach would be this: The software (Sitatex) can be set to send some messages, stored in a certain file, pre-programmed(like a cron job, or a scheduled task). So, setting Sitatex to send this message every two minutes and then changing the content of the file containing the message would do the job. But again I am stuck. Because the software uses a file format (.snd) that is stored binary. So I cannot alter the content of the file(when sending Sitatex checks the format of the file and if not ok doesn't send). I don't know how to make the binary file from the ascii file. Any ideas?
Another approach would be to track the things Sitatex does when sending the message(meabe a stupid idea). I tried to see if it keeps the message in a temporary file in ascii format while it is still being edited by the user and when he/she presses the send button it makes the binary file and sends. Got nowhere yet with this. It keeps a temp file, a draft, but in binary. When the user hits the send button, it empties the temp file, and after that I couldn't find out what happens.
Another thing I tried was to find the commands the server accepts (meabe there is something similar with the SMTP commands - you know - Hello, rcpt to, this kind of stuff). I can get access to the server that actually sends the messages. Is there any way I can "catch" the commands it receives, if there are any? So far I didn't have any success with this. The documentation I could get is very scarce and only covers the basics a user needs.

If anyone encountered a similar problem(with Sitatex or something else) or has any ideas whatsoever on this issue, I would be really grateful if shared.

Thank you.