Is a threefold divorce written in a document sent to the wife valid, especially if it was during her menstrual period, and is there a chance for reconciliation and return in this case?

If the husband utters the divorce, it takes effect, even if he did not intend it. However, writing does not effect a divorce unless there is an intention. If he utters or writes "divorce three times," only one divorce takes effect, according to the preponderant opinion. Similarly, if the divorce occurs during menstruation, it does not take effect. It is not a condition for the wife to be confronted or present to hear or know about the divorce for it to take effect. If the divorce is valid and revocable, the husband may take his wife back without a new contract as long as she is within her waiting period (iddah).