Can you explain what you mean by "tranmissions"? Is this when you call the connect method on a Transport object or when you call the send method?
I ask because it could be that you are using the static convenience method Transport.send(), which opens and closes a new connection for every message you send. You might consider reusing the connection. That is so long as your are not spoofing the from address (or changing it once you have spoofed it once)
you should be able to reuse one connection for all messages. And though your server admin probably knows better then I do - it would take a fairly miserly server config to not be able to process 100 messages.