The MMS service or "Multimedia Message Service" enables you to send pictures, sound files, video files and text.
Note: The maximum size of an MMS that you can send depends on the type of your mobile device. It may not support a 400 KB size. To know more, check the user guide of your device.
MMS Settings for iPhone:
The MMS inbox enables you to view the MMS messages that were sent to your mobile in case you are not subscribed to the service or the service settings have not been entered on the mobile. and will remain available there for 10 days.