I'm surprised no one has made any posts trying to figure out how to get hangouts MMS to work. I was super frustrated when sms first came out on hangouts because it didn't work on boost, at least not on my phone. I prefer using hangouts over the stock SMS app. I like the interface, to me it looks much cleaner and it's a step closer to having an iMessage type app for android. Anyways, I messed with this app for frustrating hours until I finally figured out how to get MMS working. In the latest update the APN settings were finally added to the app for more phones, so go to SMS settings, then APNs at the bottom, and enter a name like "boost", now the only field you're going to use and the part that frustrated me the most is MMSC, you put "http://mm.myboostmobile.com" I thought I would have to use the rest of the fields, but the rest mess it up (and I'm not sure why).