In most cases, SMS and MMS are eventually routed to a mobile phone through a wireless carrier.
Many SMS gateways support content and media conversions from email, push, voice, and other formats.
It allows SMS text messages to be sent and/or received by email, from Web pages or from other software applications by acquiring a unique identifier from the mobile phone's Subscriber Identity Module, or "SIM card".
Typically, direct-to-mobile gateway appliances are used for hundreds to thousands of text messages per month.
A direct-to-short message service centre (SMSC) gateway is a software application, or a component within a software application, that connects directly to a mobile operator's SMSC via the Internet or direct leased line connections.
The Short Message Peer-to-Peer (SMPP) protocol is typically used to convey SMS between an application and the SMSC.
They are typically employed for high volume messaging and require a contract directly with a mobile operator.
Such gateways provide their customers with a choice of protocols, including HTTP, SMTP, Short Message Peer-to-Peer and Web Services.