Every number purchased on the CPaaS platform is assigned a Voice, SMS, and MMS Request URL by default. We will be specifically discussing the SMS Request URL here. The default SMS Request URL is http://static.zang.io/ivr/welcome/sms.xml. That URL contains the following XML:
<Sms>We have received your message. Reply STOP to unsubscribe</Sms>
Every time a number with the default SMS Request URL assigned receives an SMS, we will automatically send an outbound-reply to the 'From' number of the incoming SMS with the message, "We have received your message. Reply STOP to unsubscribe".
Note: the SMS Request URL is designed to be used for testing purposes. We recommend that testing be done using an external SMS capable number/device. We do not recommend that you test SMS using two numbers purchased on our platform. That is especially the case if both numbers have the default SMS Request URL assigned to them. Doing so could cause an inadvertent SMS loop whereby the two numbers will be stuck sending outbound-replies to each other while depleting the account balance.