Bulk SMS may not deliver to any number for any of the following resons:
1. Number having DND status
2. Number not within the network covered area or switched off when the message was sent or resent by the network. Any message sent are always resent for a number of times within 24hrs before declared failure.
3. If the number is invalid. Numbers such as +2341234567890, 801234567890, 0801234567890/0809876543210 etc. Valid numbers are 0801234567890, 2348012345678, 0801234567890, 0809876543210. Numbers are separated by comma only.
4. Internet connectivity using to send message is not strong enough to complete the action.