We all live with an overabundance of e-mail. All of us have those times when we recognize that a given topic/thread is simply not of interest and we'd prefer not to read any additional content from it.
On the web interface it's easy to avoid by not activating the link for the topic itself. In e-mail it's equally easy, but it gets buried in the message footer that virtually no one ever reads.
At the end of each and every individual message e-mail you receive or each message in an HTML format digest, there is a link that allows you to mute all further content for the thread you're reading. If you search in an individual message for "Mute this topic" you should land right on the click-through link you activate to do just that. The last digest I received a few months ago used a link titled "Mute this Thread" at the end of each message presented. If you activate that link you will receive no further e-mail messages for the topic you've just muted beyond those that might already be sitting in your inbox.--
Life is the art of drawing sufficient conclusions from insufficient premises.
~ Samuel Butler, 1835-1902