Yodel shows the status of your SMS in Slack and in the message log (https://manage.yodel.io/messages). The description of each status is the following:

Outbound Message Status Progression
When sending outbound messages this is the typical sequence of statuses:

acceptedYodel has received your request to create the message from a Messaging Service. Yodel is determining the optimal 'From' number from your service.
queuedYodel has received your request to create the message. All new messages sent from a specific Yodel phone number are created with a status of queued
sendingYodel is in the process of sending the message. This status is usually only present for a very short time.
sentYodel has received a confirmation from the Super Network partner advising they have accepted the message.

Finalized message Delivery Status
After a message has been sent, the following final delivery status options are possible:

sentYodel has not received updated delivery information for your message. Typically a sent status will be replaced by a delivered or undelivered status within seconds or minutes. Once a message is older than 72 hours, receiving a further status is very unlikely. We recommend treating sent as a final status after 72 hours.

This does not mean that your text message was not delivered. Some carriers send us the information back if it was delivered, and some don't.
deliveredYodel has received confirmation of message delivery from the carrier, (and, where available, the destination handset).
undeliveredYodel has received a delivery receipt indicating that the message was not delivered. This can happen for a number of reasons including carrier content filtering, availability of the destination handset, etc.

You can try to send the message again a while later. If this still fails and you think this number should be able to receive texts, please contact us at support@yodel.io.
failedThe message could not be sent. This can happen for various reasons including queue overflows, account suspension and media errors (in case of MMS). Yodel does not charge you for failed messages.

Incoming Message Status

receivedAn incoming message has been processed, and Yodel has delivered the message to your Yodel number.