BCC addresses appearing in the To line

Split from this thread.

I just sent a circular email and put all the addresses in the BCC field, and my own address in the To field.  I had used the 'Add' icon from the ribbon, alongside the 'Check names' icon, going down the list of names and clicking twice on each to put them in the BCC field.

After sending, I got an email from a recipient to say the BCC addresses were all visible in the To field. When I looked at the Sent copy, yes, they were.

I tested it with a new email, with the Add function, clicking on the BCC field first, then on my name. My address came up IN THE TO FIELD.

I thought it might require me to first put an address in the To field, so I did that.

Then I repeated the BCC click and chose another address for me.  That too leapt up to join my first address in the To field.This is most annoying because I share everyone else's problem in that my category function for creating a group list doesn't work in live.com. Now I can't even keep names private and my job requires me to send out bulk emails.