Yes, you can, but you do have to navigate to the thread in question first, which is fairly easy to do by using the links in the emails you receive from subscribed topics. Any topic you are subscribed to will have a link at the bottom of each page that say, "Stop watching this topic." Click that and you'll stop receiving emails on that topic. There isn't any way to select multiple topics and unsubscribe from several at once though, if that's what you mean.
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I'm not likely to be around much longer. As before when I first signed up here years ago, I'm finding that after a long hiatus, and after only a few days back on here, I'm spending way too much time here again already. So I'm requesting my account be locked, banned or whatever. It's just time. Until then, well, I dunno...