How to find mails which are sent to 'undisclosed-recipients' ?

[Adam Wolfe Gordon]

Hi Vladimir,

On Thu, Jul 11, 2013 at 9:24 AM, Vladimir Marek
<Vladimir.Marek at oracle.com> wrote:
> Since my mail works in a way that it hides everything but what I
> selected to be shown to me, I was overlooking all mails which where sent
> to undisclosed-recipients. I tried to match such mails by
> to:undisclosed-recipients but that does not seem to work. Is there any
> workaround to find such mails?

I have some mail with this To header:

To: Undisclosed recipients <Undisclosed recipients:;>

I can find them with the search to:"Undisclosed recipients". Note the quotes.

-- Adam