• queued – Sprwt handed the message to the carrier and is waiting for a result.
• sent – the carrier accepted it.
• delivered – the recipient's handset confirmed receipt.
• failed – the carrier could not send it (e.g. invalid number, blocked, compliance issue).
• undelivered – it left the carrier but never reached the handset (e.g. phone off, carrier filtering).

Statuses are updated in two ways: the carrier calls Sprwt back as the status changes, and a periodic job re-checks all messages still marked queued. When a message becomes failed or undelivered the job records the carrier error code (the Sent detail page shows the code with its description) and refunds the charge once.