A message may fail to deliver due to, but not limited to, the following:
• Sending the wrong content (all languages are not supported on all phones)
• There is no known subscriber assigned to that mobile number (or the number is no longer assigned to a user).
• The phone is unreachable or turned off.
• The SMS message was caught in a Network Operator SPAM filter.
• The phone is roaming.
• Ported number/network failure.