A while back, Google added a feature to Gmail that was supposed to let you easily unsubscribe from various mailing lists, in an effort to clean up your inbox and reduce the amount of email that Google has to process. Unfortunately, the few times I’ve tried to use this (even for emails coming from a Google Group), it was a no-go, and a poor experience. However, there’s an easier way to do this, and it’s a bit less of a hassle than clicking the ‘Report Spam’ option, especially if you access Gmail from your phone (and thus likely don’t really have the spam reporting option).
It’s really simple – just search your Gmail inbox for ‘unsubscribe’. You’ll get a nice list of newsletters and whatnot that have been delivered to your inbox over the years, with the ‘unsubscribe’ link conveniently highlighted, so you can find it easily. I invested 30 minutes today on this task, and while the effects aren’t immediately obvious, it should greatly reduce the amount of junk email I get that slips through Gmail’s awesome spam filters.
In several instances, I noticed that doing it this way removed me from entire mailing lists – which is likely the reason I was getting emails from companies I don’t recall doing business with. Sure, it might be easier to just click ‘Report Spam’, but that’s not going to stop them from coming, and in many cases, these junk emails still find their way into my inbox. Unsubscribing ends them once and for all.
Ricky Cadden 
Yes, but by unsubscribing you have just told any that are spam your email is valid, so you could actually end up with more spam
Aye, definitely have to assess each case carefully. Certainly some subscriptions are handled by above board mailing list systems – but others will definitely take advantage of your 'unsubscription' to bombard you with more spam.Generally I find that if an email says “email 'unsubscribe' to blah@domain.com“, you're best off just reporting it as spam and forgetting all about it.