I'd like to also add that you have the option to have SMS/MMS automatically forwarded to an email or phone number. You could potentially have all SMS/MMS forwarded to a shared email you have with your spouse. This will ensure you can receive and view the MMS's while still responding to/receiving texts or sending MMS via SIP. I don't know how tech savvy you are, but they also have the ability to set up webhooks or callbacks. They also support SMPP