ESME

• External Short Messaging Entity (ESME) is a term originally coined to describe an external application that connects to an SMSC to engage in the sending and/or receiving of SMS.
  Typical examples of ESMEs are systems that send automated marketing messages to mobile users, voting systems that process SMS votes (Pop Idol, Big Brother etc.) basically anytime a mobile user sends/receives a message where the other party was not another real mobile user, you can be fairly sure that the other guy is an ESME.