Mobile Terminated (MT) Message is an SMS or MMS message that was terminated (sent) to a mobile phone. The message may have originated from another mobile phone or from a web server, PC or other fixed device. Mobile-Terminated SMS (Short Message Service) is capability for a mobile phone or other device to receive standard short text messages. MT-SMS is usually accompanied by MO-SMS, which is the ability to send and reply to such messages. MT Billing can sometimes, depending on regulations open up possibilities for different types of opt-in / WAP based opt-in / MSISDN billing.