A few days ago, I discovered that the iPhone converts SMS text messages sent that are sent to multiple recipients into MMS messages. It does this even if their is no multimedia content. How very annoying.
I discovered this by accident, as I was trying to text two of my kids while we were at Disneyland. Instead of getting my message, they both got a blank message that just said <subject>. As it turns out, this is how their non-MMS-enabled phones display MMS messages.
At first I though this glitch was due to my use of biteSMS, which is a very handy jailbreak messaging app. But after a bit of investigation, I discovered that this is a “feature” of the iOS messaging system, and not a bug.
Sure enough, if you create a new message, the titlebar will switch from “New Message” to “New Group MMS” when you add a second recipient. While this conversion to MMS may enable some handy group messaging features, it also means that you can’t send text messages to multiple recipients if they don’t have MMS service.
Like I said above, annoying.
Update: Problem solved. Simply go into the Setting app and turn off group messaging. You lose the group messaging (chatroom-like) functionality, but you can still send to multiple recipients — and your messages will remain as SMS as originally intended.