As you read this post, your spam folder likely just received another email. That email is now taking up space in a data center, which means it is consuming unnecessary electricity. The same goes for all of the promotions you receive and haven’t opened, or the number of email chains you’re CC’d on.

Every email sent consumes electricity. When you write an email, your device uses electricity. When you send or receive an email, that email has to use electricity to travel across a network, using both your network connection and an additional server that pushes your email to the right spot. Finally, when an email arrives and sits in an inbox, it is being stored in a database at some data center, taking up space on a hard drive and consequently consuming power.

According to calculations done by eco2greetings, a standard, text-based email has a carbon footprint of 4gm of CO2e (carbon dioxide equivalent). Adding an attachment can lift that number up to 19gm CO2e, and emails with large or multiple attachments can have a carbon footprint of up to 50gm CO2e. These numbers are backed up by Mike Berners-Lee’s How Bad are Bananas?: The Carbon Footprint of Everything, in which studies were done on the carbon footprint of emails based on specific categories.

This might not seem like a lot, but when you take into account the number of emails that are exchanged daily and annually, the carbon impact adds up fast. In 2019, OVO energy estimated that if each adult in the UK sent one less “thank you” email a day, they would save 16, 433 tonnes of carbon annually, which is the carbon equivalent of 81, 1522 flights from Heathrow to Madrid.

The following are five tips for practicing good email hygiene (and thereby helping the environment):

1. Empty your spam/junk folder regularly

   If your email provider is doing their job right, your spam emails are probably left out of sight and out of mind. Unfortunately, just leaving them alone allows them to take up space in data centers and in doing so, waste power. Making a habit of clearing this folder daily will save energy.

2. Unsubscribe to emails

   I’m going to take a wild guess that many of the automated subscriptions you receive in your inbox are left unread. Gmail makes it particularly easy to ignore promotions and other subscription-based emails with their “Promotions” and “Social” tabs. Following my previous advice on regularly cleaning up your spam folder, try picking a day every month where you go through and unsubscribe to unwanted emails.

3. Reconsider CC’ing your coworkers

   If you work in tech I’m sure this one hits close to home. Every time you CC someone on an email, you’ve sent an additional copy of that email across a network. Ask yourself, does this person really need to be on this email chain? If the answer is no, don’t do it. Not only does this help the environment, but it also saves people time.

4. Update your mailing lists

   This one is similar to my point about CC’ing. If your team at work or volunteer group changes, update your mailing list to avoid sending unnecessary emails. Just setting aside one day a month to do this will make a difference (and also annoy fewer people).

5. Reduce or shrink attachments

   The most efficient thing you can do here is replacing attachments with links where possible. If you do have to send a file, compress it first and use a lighter file format.

You might have noticed that the tips I provided for reducing the carbon footprint of your inbox are closely related to tips on freeing up mental space. Cluttered and disorganized inboxes are time-wasters and can lead to feelings of overwhelm and increased stress. Reducing the amount of email sitting in your inbox is not only good for the environment but also good for your mental health.

If you’re interested in learning more about the carbon cost of email, check out this email CO2 calculator.