You should treat a message as failed if getting one of the following errors:

Authentication error.
IP access limited.
SMS contents with sensitive characters.
SMS content is empty.
SMS content is over the length.
SMS contents are out of template.
Numbers are over the limitation.
Number is empty.
Numbers are abnormal.
Insufficient balance which unable to support the task.
Incorrect timing format.
Due to platform issue, bulk submission has been failed, please contact Admin.
Users has been locked.
Field is empty or inquiry id is abnormal.
Query too frequently.
Timestamp expires.
SMS template can not be empty.
Port program unusual.
Data existing.
Data validation exception.
Parameter exception.
Data caps.
Data unexisting.
Out of time range.
Getting fee faily.
Period total send limit.
You are sending SMS faster than the account limit .
Your request is missing one of the required parameters: from, to, api_key, api_secret or text.
The value of one or more parameters is invalid.
Your API key and/or secret are incorrect, invalid or disabled.
An error has occurred in the platform whilst processing this message.
The platform was unable to process this message
The number you are trying to send messages to is on the list of barred numbers.
You do not have sufficient credit to send the message
The number of simultaneous connections to the platform exceeds your account allocation.
This account is not provisioned for the SMS API,
The message length exceeds the maximum allowed.
The signature supplied could not be verified.
You are using a non-authorized sender ID in the from field
The network code supplied was either not recognized, or does not match the country of the destination address.
The callback URL supplied was either too long or contained illegal characters.
A signed request may not also present an api_secret.
The number you are trying to send messages to is de-activated and may not receive them.
Message was not delivered, and no reason could be determined
Message was not delivered because handset was temporarily unavailable - retry
The number is no longer active.
This is a permanent error:the number should be removed from your database.
There is an issue relating to portability of the number and you should contact network operator to resolve it.
The message has been blocked by a carrier's anti-spam filter.
The handset was not available at the time the message was sent - retry.
The message failed due to a network error - retry.
The user has specifically requested not to receive messages from a specific service.
Error in a message parameter.
A route to the number cannot be found - confirm the recipient's number.
The target cannot receive your message due to age restriction.
The recipient should ask their carrier to enable SMS on their plan.
The recipient is on a prepaid plan and does not have enough credit to receive your message
Message delivery failed because the allowed number of requests per period was exceeded.
The High Density Contact Number Range threshold has been exceeded.
Threshold has been exceeded.
Submission Control throttled.
Invalid username/password.
Out of Credit.
No route price for destination.
Receiver missing in the request.
Not enough money.