It is easier to hit delete than it is to unsubscribe from an unwanted listserv or newsletter, but if you can get into the habit of unsubscribing as you go, not only will your inbox be leaner, but so will your carbon footprint. Every newsletter generates around 10 grams of CO2, and only around 10% of newsletters are ever opened.
Read more here:
https://www.mailjet.com/blog/email-best-practices/email-carbon-footprint/