Unsubscribing from emails you don't want.
So many times I see posts here and other places online where people describe their complex filtering rules for sorting newsletters and other unwanted mailing list emails and they never bother to unsubscribe. If it's not legit spam, every mailing list email is required to have an unsubscribe link with a no-account option to unsub. It takes two clicks to stop getting the emails in the first place.