In the past, Gmail has attempted to make it easy to unsubscribe from email mailing lists, but the option has been buried under spam reporting (which may not always be what you want to do). Now, though, you can unsubscribe to many lists with a single click.
The new feature places an Unsubscribe button next to the sender’s address in Gmail when it detects that the email is coming from a mailing list. Given that this is automated, there’s no 100% guarantee that it will always work, so if you keep getting emails from a particular source, check to see if the email has its own unsubscribe process (or mark it as spam).
See the original post:
Google Adds an “Unsubscribe” Button Right to Your Inbox