I am also trying to send MMS using the SIM900. Sending SMS and MMS are totally different from my experience. MMS requires that you upload something to the module and my current problem is that I can't get the module to read what I'm putting on the UART. Perhaps I'm not putting data on the UART right, but yeah, I can't get MMS to go. If you figure it out could you post it in this thread or contact me please? ted_pham08@yahoo.com
Thanks and good luck!
Ted