Why can't Xiaomi 2s send text messages in groups?

I think the operator limited you. Your colleague sent more than 100, and the same content operator will handle it. You call the corresponding operator and say that the situation can be restored.

I suggest LZ send this kind of information separately in the future, because operators don't have time to identify whether your content is spam messages (cards) such as advertisements, so at least limit the number of messages sent at the same time per unit time ~ ~ ~ beyond this number, the SMS function will be locked!