Sent messages are not delivered sometimes

There could be several reasons:

  • The carrier of the receiver doesn't provide delivery reports;
  • Some technical issues on the side of the receiver’s carrier (like overload);
  • The message delivery to device was blocked by the receiver’s carrier due to some internal reason;
  • The destination phone number is not correct, not reachable, listed in the stop lists or does not exist;

Some information we feel will be useful for you:
—  What is the message length?
—  Can I send and receive messages with Unicode?
—  I do not receive messages sometimes
—  Sent messages are not delivered sometimes
—  Formatting international phone numbers
—  Sender ID
—  Spam