I wrote:
> The variants I've seen are
> Subject: Invitation to connect on LinkedIn
> Subject: <so and so> wants to stay in touch on LinkedIn
Actually, a bit of looking in my spam logs suggests that the best thing
would be to filter on headers that look like this:
X-LinkedIn-fbl: n-qcUUOoZC7xu6Osomtu7Puw6GhuWOdF6OrNGgqwO-6rdrXq5VwXwcd9i62mpE
X-LinkedIn-fbl: vq4Hn2B7IUfSDhzU_lQrCa-TZG-5pr8eMv_x1ajZoLQ5VeukFJ
X-LinkedIn-fbl: XWulUW6uONtHOdVFlLwD6W7gxeV-Ntn4W0rkYWXcSKh-cwWFBl
They seem to put that into all the variants...
regards, tom lane