MMS is the Mulitmedia messages service available on all modern phones phones. It is advertised as adding rich media such as images, videos, audio to an SMS message. However these messages are not just bigger SMS messages and use a combination of SMS and Data Service (Internet) to send and receive the message. As such both the sender and receiver must have Data Services available to use MMS. As with SMS, MMS is a store and forward technology and the message once sent, will be available for collection by the receiver when they next connect to the network.

The sending and receiving of an MS message is controlled by a MMSC (Multimedia messaging Service Centre). This works in an analogous method to the SMSC works with SMS messages. The message is sent to the MMSC, stored, the recipients MMSC notified that an MMS awaits, and theis then notifies the recipient which then downloads the message.

1. The message is created within the client messaging app, usually the same as the MMS app using a standard MMS Encapsulating Format which includes a combination of headers, recipients and message made up of text and rich multimedia.
2. The format of MMS messages contains
   • Header and body
   • The body is made from a number of parts
   • Each part will be one of text, image, video or audio
3. The client will send the message over the internet with the data sent via HTT POST to the local MMSC. Hence it is clear that sending an MMS relies on a data network being available.
4. The MMSC receives the message, stores it, and in the process generates a URL for the message
5. The MMSC creates a Wap Push message that is to be sent to the recipient of the MMS. This is sent to the correct MMSC for the recipient, and then sent to the recipient via SMS
6. The recipient received the Wap Push message, over SMS. Within this is the URL of the message.
7. The recipient will use the Data Network to request the URL from the relevant MMMSC
8. The data is downloaded to the recipient and the messaging app displays the message in the appropriate manner
9. If there is no data network available the app will display the URL and this can be requested to be downloaded when data network is available

It is clear that to send / receive an MMS message a Wap Push SMS message plus a a data transfer is required. Most (UK) MNO will charge the sender 55p to send an MMS. This is despite the sender having already paid for unlimited SMS messages and 4G data.