Fax API - Error List

In this article find explanations for both outbound and inbound errors you might experience with Programmable Fax. See Telnyx guidance and requirements.

1) Fax - Errors contained in the Webhook Payload:

These error details will be included in the failure_reason field contained in the Fax API Webhook event payloads. For tutorials and other details on the API Requests and Webhook payload formats, please refer to this Documentation.

• Outbound Programmable Fax Errors

Error	Description
file_size_limit_exceeded	Error from Telnyx programmable FAX Application indicating the .pdf file provided is greater in size than the prescribed limits. (i.e. bigger than 50MB)
page_count_limit_exceeded	Error from Telnyx programmable FAX Application indicating the .pdf file provided is containing more number pages than the prescribed limits. (i.e. more than 350 Pages)
fax_initial_communication_timeout	This may indicate that the call did not connect to a valid fax machine/the destination is not sending fax tones.
fax_signaling_error	Error from Telnyx Telephony Engine. Includes scenarios such as no response after sending a page, receiving a bad response to a DCS fax message, or training.
file_download_failed	The non-telephony service responsible for downloading the customer's PDF prior to initiating the fax was unable to download the file. Please ensure that there are no redirect responses (3XX HTTP); only 2XX HTTP responses will ensure we download your file and process it.
file_format_invalid	The customer file format is not PDF or is an invalid PDF.
receiver_call_dropped	Error from Telnyx Telephony Engine. The call dropped prematurely.
receiver_communication_error	Error from Telnyx Telephony Engine. It may indicate a general call failure or a telephony routing error.
receiver_decline	Error from Telnyx Telephony Engine. The destination declined the call attempt.
receiver_invalid_number_format	Error from Telnyx Telephony Engine. The destination number is not in a valid +E.164 format.
receiver_no_response	Error from Telnyx Telephony Engine. This cause is used when a called party does not respond to a call establishment message with either an alerting or connect indication within the prescribed period of time allocated.
receiver_recovery_on_timer_expire	Error from Telnyx Telephony Engine. Remote party sends a SIP 408 for an expired/timed-out call or an issue with the downstream carrier partner.
receiver_unallocated_number	Error from Telnyx Telephony Engine. This cause indicates that the called party cannot be reached because, although the called party number is in a valid format, it is not currently allocated (assigned).
service_unavailable	Internal Telnyx error. A call to another service, such as to initiate the outbound call or to retrieve the PDF for sending, failed. Could also be due to a non-typical media conversion failure.
success	Telnyx to investigate this further.

NOTE: Retries for outbound faxes, which may result in an error must be configured on the client application; Telnyx does not automatically retry faxes with errors.

• Inbound Programmable Fax Errors

Error	Description
carrier_lost	The connection to the carrier dropped while receiving the fax
fax_signaling_error	Error from Telnyx Telephony Engine. Similar to outbound error, but in reverse. Includes scenarios such as no further data after receiving a page, bad data sent from the sender etc.
received	Telnyx to investigate this further.
sender_call_dropped	Error from Telnyx Telephony Engine. The call dropped prematurely.
sender_canceled	Error from Telnyx Telephony Engine. The sender canceled the call prematurely or before the data had completed transmitting.
sender_communication_error	Error from Telnyx Telephony Engine. Can include a general call failure or a telephony routing error on the sender side.

Other Webhook Fax Errors Include:

• account_disabled
• connection_channel_limit_exceeded
• destination_invalid
• destination_not_in_countries_whitelist
• destination_not_in_service_plan
• destination_unreachable
• invalid_ecm_response_from_receiver
• no_outbound_profile
• outbound_profile_channel_limit_exceeded
• outbound_profile_daily_spend_limit_exceeded
• receiver_incompatible_destination
• receiver_no_answer
• user_busy
• user_channel_limit_exceeded
• fax_initial_communication_timeout

2) Fax - Errors in the Fax API CDR

These error codes and messages are contained in the last 2 columns in the CSV file generated by the Telnyx Portal Reporting Section, specifically, when selecting "Report Type": "Fax API".

• https://portal.telnyx.com/#/reporting/detailed-records

Result Code	Message
0	OK
2	Timed out waiting for initial communication
3	Timed out waiting for the first message
5	The HDLC carrier did not stop in a timely manner
6	Failed to train with any of the compatible modems
13	Unexpected message received
14	Received bad response to DCS or training
15	Received a DCN from remote after sending a page
17	Received a DCN while waiting for a DIS
20	Received no response to DCS or TCF
23	Invalid ECM response received from transmitter
31	Timer T2 expired while waiting for fax page
32	Timer T2 expired while waiting for next fax page
48	Disconnected after permitted retries
49	The call dropped prematurely