You can already quickly unsubscribe from undesired newsletters in gmail by clicking on the small arrow near the sender/receiver contact details and clicking on

You can already quickly unsubscribe from undesired newsletters in gmail by clicking on the small arrow near the sender/receiver contact details and clicking on the "Unsubscribe from this sender" link. It seems like most (all?) of the times it sends back an empty email with "UNSUBSCRIBE" as its subject, which most newsletter mailing system correctly interpret as an unsubscription request. The approach described in the article is somewhat orthogonal to this, in that it scans the email for the unsubscribe link, so it's still not useless, I guess they complement each other.