I understand this concern.

But the problem is how you will decide which language to use when the new user joins?

There can be put a language button as question when register for example

That can be done. But its not in scope for this plugin and so only this can't be done.

Oxwall has a language setting. The message is not found there like it should normally be so that people can receive messages in their languages

See, you did not understand my point.

When an user newly registers, this plugin sends our the message automatically as soon as the user registers.

At that point of time, the site will be in only 1 default language. There is no way to determine what language that the newly registered user will want to see the message.

I am with Oxwall for several years. I know very well that Oxwall has a language settings. But this does not related to what you expect.

Hello. Can we choose language based on IP code of newly registered user?

Can you please explain the logic if you anything in mind for this?

BTW, please create a new post if you have anything in mind. It will help to monitor those threads easily.