I'm just trying to nail down the problem, not pointing fingers at anybody. Some of you know how crazy your web clients can get when something stops working correctly. My client in this case is using email at his domain, so no Yahoo, Gmail, etc. are involved.
Fast Secure Contact Form is a *wonderful* plugin, makes my life much easier. Chad, please do report back after you test with the latest WP version. Thanks to all who have responded. Hoping to get this working through a great forum community of people who are a ton more knowledgeable than I am!
BTW, the site is http://www.williamhudsonattorney.com. The opt-in in the sidebar immediately sends the user a canned email but ignores a BCC email to the owner, so he has no way to find out who is requesting his promotional free material. The contact form on the 'contact' page of the site does not work at all, I and others have filled out the form several times and my client gets nothing in email. I set up all the parameters per the tips listed in this thread, even the unused default forms in the plugin....still nothing.
Any ideas would be greatly appreciated!