When i was back home in the Philippines i have signed a few authorization letters with my old maiden name after i have just filed a Report of Marriage with my new last name at the Philippine Embassy in New York a month after that. Will those letters be accepted by the companies they will be submitting it too?
The reason for the letters were when our mother will file our deceased father's life insurance all the money will just be refunded to her and she will just give our shares after she gets it to her account.

I think there would be no defect in those authorization letters because those documents were executed properly and with authority. It would be nice thought to send an update on your status on the corporations to avoid confusion on future deals or transactions.