NowSMS can be configured to send MMS messages using two different delivery mechanisms. Before we explain these two different options, it is best to explain a bit about how MMS actually works.

MMS messages are delivered using a combination of SMS and WAP technologies.

When a mobile phone receives an MMS message, what it is actually receiving is an MMS notification message which it receives over SMS (WAP Push). This MMS notification message contains header information about the MMS message, and a URL pointer that the recipient must fetch in order to retrieve the content of the MMS message.

This URL pointer is a dynamically generated URL for the MMS message content which is stored on the MMSC. In a typical phone-to-phone MMS transaction, the process of sending and receiving the MMS message works like this:

• The sending phone initiates a data connection that provides TCP/IP network connectivity, usually over GPRS.
• The sending phone performs an HTTP POST to an MMSC of the MMS message encoding in the MMS Encapsulation Format, as defined by the Open Mobile Alliance (http://www.openmobilealliance.org). The encoded MMS message includes all of the content of the MMS message, as well as header information, including a list of intended recipients for the message. (Note: In most environments, the HTTP POST will be routed through a proxy server. Some devices will use wireless profiled HTTP and TCP through a WAP 2.0 proxy server, while other devices will use the Wireless Session Protocol, WSP, through a conventional WAP proxy server/gateway.)
• The MMSC receives the MMS message submission and validates the message sender.
• The MMSC stores the content of the MMS message and makes it available as a dynamically generated URL link.
• The MMSC generates an MMS notification message, which is sent via WAP Push over SMS to the message recipient(s). This MMS notification message contains a URL pointer to the dynamically generated MMS content.
• The recipient receives the MMS notification message. It then initiates a data connection that provides TCP/IP network connectivity (usually over GPRS).
• The recipient phone performs an HTTP (or WSP) get to retrieve the MMS message content URL from the MMSC.

When you send an MMS message with NowSMS, this can be done using either of the following configurations:

1. Direct MMS delivery. In this configuring, NowSMS is an MMSC. The MMS message content is stored on the Now SMS/MMS Gateway, and the gateway publishes a dynamic URL for access to the MMS message content. The gateway generates an MMS notification message to the recipient device which is sent over SMS, and this notification includes a URL pointer back to the MMS message content on the NowSMS server.
2. Send the message through the operator MMSC. NowSMS supports all of the major MMS related protocols, including MM7, MM4, MM1 and EAIF for this purpose. But most frequently, what we see is the use of MM1 where NowSMS makes a GPRS connection over a GSM/GPRS modem, connects to the operator WAP gateway that is designated for MMS usage by the operator, and submits the message to the operator MMSC via the WAP gateway over the GPRS connection. (The operator MMS gateway then generates the dynamic URL and MMS notification message that is ultimately received by the recipient device.)

The default configuration of NowSMS is to use approach #1 (Direct MMS Delivery as an MMSC). When you perform direct delivery, the receiving MMS client needs to be able to connect to the NowSMS server in order to retrieve message content. In this case, it is important that the MMSC HTTP Port of the NowSMS server be accessible either over the internet or over the relevant mobile operator network(s). It is also important that the "Local Host Name or IP Address" configuration setting of the NowSMS MMSC be configured to a host name or IP address that is externally accessible. Some additional discussion of these settings can be found on the NowSMS Discussion Board at the following link: http://www.nowsms.com/discus/messages/485/1958.html.

The problem with approach #1 (Direct MMS delivery) is that the MMS client on every mobile phone is configured with settings for how the phone sends and receives MMS messages. To send or receive an MMS message, the phone makes a GPRS connection (to a GPRS APN). It then usually connects to the MMSC for sending/receiving messages through a WAP proxy/gateway. The pre-configured MMS settings on many mobile operator networks are setup to connect to a special MMS-only GPRS APN which connects to an MMS-only WAP gateway ... and this GPRS APN/WAP gateway is configured only to allow connections to the operator MMSC. If the recipient mobile phone is subscribed to an operator that has this type of setup, and you attempt direct MMS delivery, you can send the MMS notification to the phone over SMS, but the phone cannot retrieve the MMS message from your server because the GPRS APN/WAP Gateway does not allow it.

In those cases, the only alternatives are:

• Use approach #2, and submit the message through the operator MMSC. Additional information on this type of configuration can be found at the following link: http://www.nowsms.com/documentation/ProductDocumentation/mms_notifications_and_content/Connecting_to_operator_MMSC.htm
  
  Do note that you will need to determine the appropriate connectivity settings for connecting to your operator MMSC over GPRS. Settings for many mobile operators can be found at the following link: http://www.nowsms.com/discus/messages/485/491.html
• Change the settings in the receiving mobile phone so that it can receive messages from external MMSCs. (This is usually just a matter of changing the GPRS APN and WAP Gateway IP address that is defined for the MMS client ... change them to match the similar settings already configured for the WAP browser.) Note that in doing this, you may no longer be able to send/receive MMS through the standard operator MMSC.
• Use an altnerative to MMS, such as the multimedia WAP push function in NowSMS, where the multimedia objects are pushed to the WAP browser in the phone instead of the MMS client. (NowSMS can be configured to convert a submitted MMS into this format for delivery.)