Messages and campaigns each carry a status, and they are separate vocabularies. A campaign can be complete while some of its messages failed.

Message statuses

These appear on individual messages in SMS Management.

Sent versus delivered

SENT means the mobile network accepted the message. DELIVERED means it reached the handset.
Most messages settle at SENT and never progress to DELIVERED. That is not a fault and does not mean the message failed — it reflects how much confirmation the network returns. Treat SENT as success.

Statuses that mean you should act

A whole campaign showing FAILED usually means a credit or sender ID problem. A scattering of failures among successes usually means bad recipient numbers, particularly if they were pasted in manually rather than imported.

Campaign statuses

These appear on the campaign row rather than on individual messages.
COMPLETED means the campaign finished working through its recipients, not that every message succeeded. Expand the campaign to check per-recipient results.

Reminder statuses

On the Events tab of Calendar Reminders. An appointment with no status at all means no rule matched it, which is different from a reminder that failed.

Approval statuses

Sender IDs and keywords share one shape.