Vivoz3i sent a text message to someone else, and the other party received it. What does it mean that a red exclamation mark appears on the date of texting a few days later?

You texted him earlier, and the other party received it. When you send him a text message a few days later, there is a red exclamation mark, which represents your information. I can't send it to the other party's mobile phone now.

There are two possibilities for this situation. One possibility is that the other party's mobile phone has been cancelled now.

The second possibility is that the other party blacked you out, so there is no way to send your message to the other party's mobile phone.