Advanced guide to unsubscribing from an ACS marketing list

I used to think I was pretty good at avoiding spam. I always tick the box (or sometimes untick it - you have to be on your toes) that stops companies sending me marketing 'literature'. It all worked well until I met the ACS...

You see, I did tick that box with the ACS (I've just checked) but the spam keeps coming. And there's isn't just one list - oh no, they have got lists for authors, conference attendees, everything and anything. They used to send me a pre-approved membership form even though I was already a member! Naturally I complained, someone responded, and I continued to receive the requests. So it goes. I subsequently moved countries - seems to have worked.

So...back to the main topic. Today I received an email from marketing@acs.org about something called ACS Spam (I'm summarising some details here). As required by some internet law (in the US?), they include the following helpful unsubscribe link at the bottom of the email:

If you do not wish to receive any further correspondence from ACS via email, please send a blank e–mail to purge-allcontributors2010-7753700d73f2fd1010f8a0584006fffc5bb2fdf@listmanager1.acs.org and send the message.

Apart from the fact that the sentence doesn't make any sense, it simply doesn't work - and I've tried it before for other ACS spam. Here's the response I received:

Delivery to the following recipient failed permanently:

purge-allcontributors2010-7753700d73f2fd1010f8a0584006fffc5bb2fdf@listmanager1.acs.org

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 ... Hostname of recipient unknown to Lyris ListManager (state 14).

State 14, eh? This means that the ACS wants to play hardball (hurling perhaps). I was about to email the ACS directly, when I noticed a feature of Gmail I hadn't seen before. If you click on "Show Details" for the original email, you will see a link for "Unsubscribe me from this sender". And believe it or not, clicking on this appeared to work. I got an email back from "Lyris ListManager" saying that I had been subscribed from 'allcontributors2010'. This appears to be a Gmail only feature (see this blog post) so good luck unsubscribing if you use a different email provider.