How does Unicom send international short messages?

The method of sending international short messages is as follows: 1. If you send a short message to Taiwan, Hong Kong, Macao and other countries or regions except Chinese mainland during domestic or international roaming, the sending format is: 00+ country code+other party number; 2. If you send a short message to Chinese mainland during international roaming, please enter the number of the other party directly in the sending format.