Before CFPB got a hold of Reg B, back when the address was 201.whatever--where do I find the what used to be 201.17-Requirements for electronic communication?

It was 12 CFR Part 202. You may recall that the Fed rescinded that section of the regulation in, if memory serves, 2007. It was, in fact, 202.16. So you have to go to the GPO's website and link to its Federal Digital System (fdsys) resource, find the link to the Code of Federal Regulations and then pull up the info available for 2007, Title 12, and keep clicking the + signs in the left column to expand things until you expand Part 202. You can pull down section 202.16 as a PDF document.

To save you time, here's a link straight to that PDF: http://www.gpo.gov/fdsys/pkg/CFR-2007-title12-vol2/pdf/CFR-2007-title12-vol2-sec202-16.pdf

None of that requirement is operative any longer. As I mentioned, it was rescinded in 2007 (you'll find that the section is gone if you tried finding it in the 2008 CFR version).

I see, so it hasn't moved over to Reg E? Thank you very much!

Comparable rules were included in several of the most popular consumer protection regs. They were a bad idea and, fortunately, all were trashed.