What does SMPP mean?

Short Message Peer-to-Peer (SMPP) is a protocol used by operators to process and transmit high volumes of SMS text messages. Due to the low overhead high volume messaging is possible.

Although BudgetSMS does not yet support SMPP for its customers, the HTTP API can also be used for high volume messaging.

See also: https://en.wikipedia.org/wiki/Short_Message_Peer-to-Peer