Some SMSC does not support SubmitMulti. Please ask them if this message allowed to you. I found out that to be the case in my situation. Thanks for the heads up. I also noticed that the client automatically generates a value for the Sequence property. That's proactive. Thanks for the prompt response.

I tried using Submit with SubmitMulti, but the only response is GENERIC_NACK. My code is in Boo (http://boo.codehaus.org), a Python-like .NET language. I'm using the interpreter, and also copied the output (output lines DO NOT begin with >>>: >>>import ALT.SMS >>>c = SmppClient() ALT.SMS.SmppClient ...