# The carbon cost of email — Impact & methodology

Email feels weightless. At scale, it isn't. The good news: stopping the newsletters you never open is one of the easiest footprints to cut. DontMailMe is funded by pay-what-you-want donations, and half of every donation plants trees via One Tree Planted.

## The numbers (sourced)

- **~29.7 million tonnes** of CO₂e from spam email each year — more than some entire countries emit (Today Testing).
- **84.8%** of all email sent is spam — about 271 billion messages a day (Today Testing).
- **~40 kg** CO₂e for one newsletter sent to 10,000 people who mostly never open it (10,000 × ~4 g).
- **~184 kg** CO₂e from email for a typical office worker per year (Mike Berners-Lee, *How Bad Are Bananas?*, via Carbon Literacy Project).

## How we calculate your impact

The home-page calculator uses transparent assumptions:

- **~2 emails per week, per newsletter** → ~104 emails/year avoided per unsubscribe.
- **~4 g CO₂e per promotional email** — the Carbon Literacy Project's "standard email" figure (range: 0.3 g spam to 50 g with a large attachment).
- **~0.16 kg CO₂e per km driven** — average passenger car, for the "driving avoided" comparison.
- **~20 kg CO₂ absorbed per tree per year** — One Tree Planted's working figure.
- **~€5 donated plants one tree** — half of each pay-what-you-want gift goes to One Tree Planted (~€2.50/tree); the other half funds the project.

So unsubscribing from 20 newsletters ≈ **2,080 fewer emails/year** and ~**8 kg CO₂e** not emitted — every year, automatically.

## An honest note on the numbers

- **Unsubscribing stops *new* mail.** It doesn't by itself free storage you've already used — for that, delete old mail and empty Trash/Spam.
- **The saving is "emails never sent," not a one-time delete.** Critics note the energy to delete an email can exceed its own footprint; we count prevented future sends, a recurring saving.
- **Estimates are estimates.** We use mid-range, sourced figures and show our working.

The point isn't guilt. A cleaner, calmer inbox happens to be good for the planet too — so the good part comes along for free.

*Last updated: 17 June 2026. Sources: Today Testing, World Cleanup Day, Carbon Literacy Project, One Tree Planted, Mailbird Email Overload Survey 2025.*

Related: [How it works](https://dontmailme.org/how-it-works.md) · [FAQ](https://dontmailme.org/faq.md) · [Set up Gmail](https://dontmailme.org/gmail.md)