This article explains the meaning of common response codes found in Voice and SMS alert delivery reports.
📱 SMS Message Errors
| Response | Description |
|---|---|
| Message cannot be sent with the current 'To'/'From' | The sender ID or number type (e.g., shortcode) is not allowed for that number. |
| Shortcode not supported by carrier | The recipient’s carrier does not support receiving messages from shortcodes. |
| Destination device may be a landline | SMS was sent to a landline that cannot accept text messages. |
| Device switched off / unavailable | The device was off, out of service, or unreachable. |
| Number is no longer active | The number has been disconnected or is no longer in use. |
| Destination number unknown | The number is invalid or not recognized by the carrier. |
| Unknown error: 30008 / 30500 | Catch-all error when the carrier provides no specific reason for failure. |
| Pending Carrier Result | Message was sent but no final status was received from the carrier. |
| Blocked number | The number has opted out or was blocked by the system or carrier. |
| Carrier unreachable / shortcode unsupported | The destination carrier cannot receive messages from this sender. |
| Invalid number | Disconnected, incorrectly formatted, or inactive number. |
| TLS/SSL connection error | Secure connection to the messaging platform failed. Backend issue. |
☎️ Voice Call Errors
| Response | Description |
|---|---|
| Declined / Rejected | The call was actively declined by the recipient or blocked by the carrier. |
| User Busy | The recipient was already on a call or had "Do Not Disturb" enabled. |
| Temporarily Unavailable / Service Unavailable | The call could not be completed; recipient’s device or carrier was unreachable. |
| Destination number is invalid | Number is not assigned, no longer active, or malformed. |
|
Number not found / Does not exist |
Number is unassigned or no longer exists with any carrier. |
| TimedOut | Call attempt timed out without a response. |
| No Answer | The phone rang but was not answered. |
| Call Failed / Hangup | The call was dropped or terminated before completion. |
| Circuit Congestion / Network Busy | Carrier network was overloaded and could not complete the call. |
| Hangup at: X secs | The call connected and ended after X seconds (often due to voicemail or user disconnect). |
| Full message delivered | The full audio message was successfully played. |
| Originator Cancel | The call was cancelled by the system before it connected. |
| CPS Limit reached P | The system hit a call-per-second (CPS) limit. Some calls may be delayed. |
| Invalid Number | The number is disconnected, misformated, or inactive. May also appear as “Unknown,” “Not Found,” or similar. |