Does a divorce take effect merely by writing a mobile message with the wording: "If you don't tell me about something, then you are divorced," without sending it, and with the intention of not sending it and merely venting anger?

Divorce in writing does not take effect unless the husband intends it. Conditional divorce does not take effect unless the condition is met. Accordingly, divorce in this case does not take effect due to the absence of intent to divorce. And even if the intent were present, the oath has not been broken.