Want to explain how you are trying to send your MMS? Then we can tell you perhaps what you are doing incorrectly.
The easiest way I find to send a MMS is to long tap on the file I want to send and pick handcent as my messenger. Then type in the info and send it off.
I'm going to throw something out there. Is there a file size restriction for Handcent? Reason I ask is, while my wife was in Texas with our daughter, I was taking videos of our son for her. I couldn't get them to send. I also noticed on the camera there are a few options for taking video and one of them is mms video. SO I was thinking file size limit or just some kind of formatting issue.
I don't mind I dont know how to send it I meant it won't send it. I would send a text after trying to sending mms and the text would sent but the mms still is trying to send