On Thu, 08 Apr 2010 14:28:20 -0700
Carl Worth <cworth@cworth.org> wrote:

>   2. A "list:" prefix to match content from headers that identify
>      mailing list. My perception is that there are likely a handful of
>      different headers that have been used, and they should all be
>      indexed so that "list:" will search any of them.

Almost all modern mailing list software seems to use List-Id:

    https://tools.ietf.org/html/rfc2919

-- 
Mike Kelly