Retry refers to the process of the SMSC retrying to deliver an SMS message that failed to be delivered during a time period the message is valid, which is usually 48 hours. If a delivery of a message fails the SMSC starts a retry procedure that tries to deliver the message periodically.
Voice message delivery can also be retried during the message validity period (up to 48 hours). Retry for Voice messages is handled by Infobip based on the customer desires. Custom retry periods between the calls can be set along with the number of retry attempts.