At The New York Times, Bob Morris says an email note is more and more considered acceptable for some thank-yous.
Even back then, Ms. Post acknowledged that letter writing was a chore.
Today, those who hate writing thank-you notes will be pleased to know that for dinner parties, even sticklers suggest you have to write them only if there was a written invitation.
And it has become more acceptable to phone or send an e-mail message of thanks, too, as long as it’s not from a cab two minutes after leaving. The point is to tell a host that the evening has lingered pleasantly in your mind, that it wasn’t taken for granted.
He covers all the bases, though. He later writes that it's best to send a note—
“But I don’t think you can ever write too many thank-you notes,” said Hilka Klinkenberg, whose firm, Etiquette International, advises business leaders. “At a time when everything is so fleeting, nothing has an impact like something handwritten.”
I’m with her. I love a good thank-you, agenda-laden or not. That’s why I eventually sent my hosts thanks for their great dinner.