I do believe there is legislation that if an email leaves the senders server and makes it to the recipients server it is deemed to have been sent.
Transport and Main Roads in Qld are of that opinion.
That includes snail mail.
They take no responsibility of non delivery on mail and AustPost will not take responsibility for non delivery.
As Mr Plod said to me, "You do know that you can get registration renewal notices sent by email" as he wrote out a ticket and then sent a permit to drive an unregistered vehicle to my home address via a text message.
I nearly replied "Why should I change from snail mail, which had failed only once in 60 years, to email delivery of unknown reliability"