The difference between delivery and sending.

Sending means that the short message has been sent normally from the sender, but the receiver may not be able to receive it at this time. Delivery means that the receiver has successfully received it.

There is always a short message center number in the setting of short message function in mobile phone. We send a short message, which is actually sent to this short message center first, and then sent to the users at the specified number through it, which is equivalent to passing through a transit station dedicated to processing short message data. Sending only means that the short message has arrived at the short message center, and sending only means that the whole sending process of the short message is successful.