China Unicom blocked the release of short messages.

Lifting the SMS blacklist: If sensitive words are not involved, you can contact customer service to lift the ban. If sensitive words such as illegal words are involved, you can bring the original ID card to the nearest business hall and sign a letter of commitment to apply for lifting the ban. You can only apply for lifting the ban once a year. If it is intercepted by the system again, it cannot be opened. I suggest you modify the content of the message later before sending it.