If there is a problem with text message delivery, Mongoose will display an alert indicating that a delivery issue has occurred:
Clicking on Not delivered will show details on the delivery issue. Typically, delivery issues are related to invalid/disconnected mobile numbers or a landline number listed as a mobile number on a contact's record.
Note: To reduce and avoid the occurrence of delivery errors, you can enable the Phone Number Validation service (if not already enabled).
Here is a list of possible issues that could cause delivery problems:
| Code | Error Message |
| 11751 | Media exceeds carrier size limit. |
| 12300 | Media type is invalid. |
| 21211 | The message could not be delivered. It is likely that the receiving number is not a valid mobile number. |
| 21217 | The message could not be delivered. It is likely that the receiving number is not a valid mobile number. |
| 21408 | This message could not be delivered, as the region this mobile belongs to has not been enabled. Please contact support@hellomongoose.com. |
| 21610 | The recipient's number cannot receive messages because it is on an opt out list at our SMS gateway. |
| 21612 | This number is not currently reachable via |
| 21614 | The message could not be delivered. It is likely that the receiving number is not a valid mobile number. |
| 21623 | Too many media uploads |
| 30001 | Unable to deliver message due to an undetermined issue. Please contact support@hellomongoose.com. |
| 30002 | Unable to deliver message due to an undetermined issue. Please contact support@hellomongoose.com. |
| 30003 | The recipient could not be reached. The mobile handset may be in a poor coverage area or without access to the network. |
| 30004 | The recipient's number is blocked from receiving messages and may be blacklisted. |
| 30005 | The recipient's number does not exist. |
| 30006 | The recipient's number is a landline or is associated with an unknown carrier. |
| 30007 | The message could not be delivered due to the carrier's content-based spam filtering. |
| 30008 | The message could not be delivered due to an error. The receiving number may be a landline or associated with an unknown carrier. If sending an image, please ensure the file type is correct. |
| 30009 | Please contact support. |
| 30034 | Unable to deliver message due to unregistered campaign carrier message filtering |