Email - Undisclosed Recipients

How do I put "undisclosed recipients" in my To: box when sending emails to lots of people?

I know how to use the Bcc field to hide the recipients' names but don't know how to do the above.

I've sent to myself which kind of solves it. I receive some emails with "undisclosed recipients" in the To: box. I could ask those people how to do it but I don't know them personally and they're sending the stuff from their work.

Thanks.

Wouldn't you have to save them as a "group" in the addy folder firstly, and then pick the "group" and auto place in the BCC field when forwarding?

Do you also delete the addy of the sender of the email when on forwarding? I do, but despite asking my recipients individually to do the same, they don't (except a few) and it didn't take long for spam to hit the new account I set up to avoid it.