You are incorrect. The copyright law has changed. It USED to be that you had to post a copyright notice for there to be a copyright. Publishing something without such a copyright notice could invalidate a copyright claim, as some publishers discovered to their horror.

HOWEVER -- that law has CHANGED. The new law says that anything you write is considered copyrighted unless you say otherwise. That's why you see those "creative commons" notices on some websites and documents.

So please don't post emails without permission from the writer.
It's also just polite and common sense. I'm not talking just about Mr. Ehrlich, lots of people don't want their emails published -- which posting them on a website is.