Why do some SMS recipients see a Sender ID that is not my Twilio number?

Some carriers in certain countries will block SMS that are sent from foreign phone numbers. To make sure your messages get through, the Sender ID of a message may sometimes be modified to a format that will be accepted by the carrier of the mobile device.

Messages where the Sender ID was modified do not support 2-way communication as replies from recipients will not be routed back to your Twilio number.