My mobile phone number is five seven zero zero. According to my SMS report, the sending was unsuccessful because of the delay. What happened?

The message that SMS sending is suspended usually comes from the number that does not support arrival prompt (such as special service number, etc.). ) or the SMS service center is busy, which does not necessarily mean that the message has not been sent. For these messages, we can only judge whether they have been delivered according to the other party's reply. Similar sending reports may appear when some users are turned off or users are not in service area.