When sending SMS messages, it is possible that some messages do not reach their recipients and bounce. This document explains the different types of SMS bounces that can occur and their causes:
- Call barred by operator This message is usually given when there is some kind of restriction on the destination line that prevents SMS delivery. For example, a prepaid user who has run out of credit and has the line temporarily blocked waiting for a recharge.
- Failed Message Delivery This is the generic error, when the operator does not give us more information about the reason for the error.
- Ported Number This code is actually used for "Unknown or ported number", i.e. when a number has been ported to another operator to which SMS cannot be delivered (not possible in Spain) or when the number has no active line (the number exists, has a correct format and is assigned to an operator, but does not correspond to any user).
- Validity Period Expired The message expires without being delivered to the terminal due to a temporary problem with the terminal, such as being turned off, out of coverage or with a full inbox.
The following is a list of the different statuses returned by the operators:
- Delivered to destination: The message has been delivered to the destination terminal.
- Sent: The operator is trying to deliver the message but the destination terminal has no network or is turned off for delivery. By default, the operator is trying to deliver the SMS for 48 hours.
- Terminal unavailable: After 48 hours if the terminal has not recovered the network, the operator gives up its retry policy and returns this status.
- Message not delivered: In this case the operator has not been able to deliver the message, but does not give more details. It is usually because the phone is deactivated or the incoming messages are restricted, broken or the mailbox is full.
- Error: Invalid phone: The number does not have a valid format, for example 8 digits for Spain. The sending has not been done and nothing has been charged for it.
- Error: Error when sending: This status indicates that the operator has rejected the sending, usually because the number is not valid.
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