Paul: Maybe he lost your email address.
This can happen.
Jane: Why do you think he has stopped writing to me?
Paul: How should I know why he has stopped writing to you?
Jane: I am sure the girl is the reason why.
Paul: There could be other reasons why he does not write.
Jane: Like what, for example?
Paul: Maybe your brother is angry with you for some reason.
Jane: That is no reason.
At least, it is not a good reason.
Paul: There could be many different reasons why he does not write to you.
Jane: Why do you say that there are many reasons?
Paul: I am just trying to help.
You need not worry about him.
