我曾分析过 outsourcing seo 服务的弊端，here is another negative case of outsourcing email marketing.
I received a newsletter from Tesco today, and happened to click on one of the embedded links. (I am not a newsletter reading fan. I seldom click on embedded links.)
I got a “404 Not Found” error when I natigated to that url. After a few seconds, I became aware Tesco link tracking system is hosted on http://ad.doubleclick.net/, which is on my black list. I assume Tesco have a third party doing email marketing for them, otherwise Tesco on their own have no reason to use ad.doubleclick.net as a click tracking provider.