Carbon footprint of an email: decoding an underestimated environmental impact
Written by Tony Demeulemeester, Co-founder & COO @ Eli
January 5, 2026 · Updated January 23, 2026 · 14 min read
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In 2026, more than 375 billion emails will be sent every day worldwide, according to Statista. If each of these emails were a grain of rice, all the emails sent in 2025 would be enough to cover the whole of Paris under 42 cm of rice…
Among all emails sent, around 25% will contain an attachment, and these emails alone will account for 98% of the total volume of data sent by email, according to a study by Osterman Research.
At the same time, it is estimated that on average 75% of a company's intellectual property is contained in its emails and their attachments: the issue is not only one of impact and digital pollution, but also of security, and sometimes of governance and sovereignty. At Eli, we continuously support our corporate clients in engaging their employees on responsible digital topics while measuring the success and impact of the actions deployed, and our statistics are clear: there are many digital sobriety levers for employees, and email use is a major one! (more info here)
What is the carbon footprint of my emails?
It is important to consider the total carbon footprint of your emails, but you also need to understand where the carbon footprint of an email comes from. To quickly answer the question “what is the carbon footprint of my email?”, the French Agency for Ecological Transition (Ademe) gives us two statistics:
An email emits on average 4 grams of CO2 over its entire life cycle
An email with an attachment emits on average 35 grams of CO2 over its entire life cycle, i.e. 7 times more!
We can note that the digital pollution of a single email remains low compared to the average carbon footprint of a meal (2 kg CO2) or a 10 km car journey (2.1 kg CO2). But the number of emails sent and received is already very high and keeps increasing, which makes digital pollution grow year after year.
These statistics should nevertheless be taken with a grain of salt, since the data uncertainty is 100% – this means the pollution of each email is specific.
In this article, we will look precisely at the journey of these emails and their attachments, and in particular where they are stored, from the sender to the recipients, to better understand the complexity of an email’s carbon footprint and its impact on global warming.
To do this, we will project ourselves into a typical scenario: I have a corporate email inbox managed by Google (as is the case for 3 billion people worldwide), and I send an email with an attachment to 3 recipients whose inbox is managed by Microsoft Outlook via Office 365 (as is the case for 400 million people worldwide).
The journey of my email
The journey of emails can be broken down into 3 stages:
From my computer to my mail server
From my mail server to my recipients’ mail servers
From my recipients’ mail servers to my recipients’ computers
At each of these stages, my email will travel a path comparable to that of a postal letter: it will pass through many “roads” (fiber optic cables) and “sorting centers” (servers, routers, switches, etc.). In addition, sending and storing these emails requires considerable energy, particularly through the use of data centers. These data centers account for a significant share of global energy consumption and contribute to greenhouse gas emissions, which illustrates the importance of taking the carbon footprint of emails into account in discussions on ecology and sustainable development.
Just like a postal letter, the actors in charge of routing emails will look for the most optimized path so that it arrives safely as quickly as possible. However, it may take certain detours to pass through large sorting platforms which, unlike postal letters, may route emails back and forth multiple times between Europe and America.
But let’s take a closer look at the storage of my email and its attachment: unlike a postal letter, it will in fact be duplicated (and stored) many times before reaching its recipients. The environmental impact of my email will therefore be multiplied.
Journey of my email with attachment:
I have written my email and added my attachment, initially stored on my computer. One copy.
I click on “Send”. My email is then sent to my mail server (hosted by Google, in my case), where it is stored. 2 copies.
For data security reasons, Google will duplicate my email in 2 other storage zones: if my main server is affected by a fire, the backup mail servers will take over. 4 copies.
My email is then sent to my recipients’ mail servers, where it will also be duplicated for backup. I send my email to 3 recipients, also generating 2 x 3 additional backup copies. 13 copies.
My email finally arrives on my recipients’ computers: hooray! My recipients use their inboxes from their computers, but also from their smartphones. The attachment in my email is automatically downloaded to all of my recipients’ devices: 6 times. 19 copies.
I also obviously have a smartphone on which my inbox is connected. My smartphone therefore also downloads my email. 20 copies.
If my email is then forwarded by my recipients, the same pattern will be repeated with 5 new copies generated for each new recipient (one copy on a smartphone, one copy on a computer and 3 copies on servers – and digital pollution that keeps growing…).
What happens next: an eternity of storage and digital pollution
We saw in the previous section that the attachment of my email sent to 3 recipients ended up existing in 20 different copies: 4 copies on computers, 4 copies on smartphones, and 12 copies on servers (including 8 backup copies). This prolonged storage contributes to the increase in greenhouse gases.
So, what is my attachment? It is a simple purchase order sent to a client (their Purchasing, HR and CSR departments), from whom I am expecting a signed copy in return. This purchase order has a validity period (like any purchase order), which I set at 45 days. In 45 days, this document will therefore no longer be of any use! This unnecessary storage also contributes to global warming.
And what if it were a visual for a future LinkedIn post scheduled in a week? That email and its attachment would then no longer be of any use once the visual is published on LinkedIn, in 7 days.
You will have understood: in the vast majority of cases, the attachments in our emails are only useful for a very limited time. Yet we store them for a long time. A very long time. While continuously emitting greenhouse gases.
Storage and carbon footprint on my smartphone and my recipients’ smartphones
Here, in my case, the issue is simple: storing my email and its attachment on my smartphone is totally useless to me: I do not intend to access this file on my phone, and its storage could be avoided. The same goes for my email recipients, who sometimes read their emails on their smartphones without actually opening the attachments.
Fortunately, our smartphones will automatically delete these copies after a few days to optimize the available space on our phones.
Here, to limit the impact of my emails, it would have been far better if these emails and their attachments had never been needlessly downloaded to our smartphones.
Storage and carbon footprint on my computer and my recipients’ computers
These copies are by far the most legitimate: I want to keep my file on my computer, and my carefully chosen recipients are certainly interested enough in my file to store a copy. However, it is important to note that the digital storage of attachments can have a carbon footprint similar to that of printing on paper, due to the carbon pollution emitted when producing the energy needed to power the servers and storage devices.
Ideally, however, I would like to make sure of two things:
My file is not stored unnecessarily on the computer of recipients who do not feel concerned by its content
This file does not remain stored on these computers under conditions that are beyond our control
Unfortunately, since we all use email software that manages storage autonomously (Apple Mail, Microsoft Outlook, etc.), my file will be stored on my computer and on my recipients’ computers for several years, well beyond the period during which its storage is truly useful, inevitably causing unnecessary carbon impact.
Storage and carbon footprint on my mail server and my recipients’ mail servers
This is where we witness the greatest possible waste of resources, the greatest digital pollution, and the greatest governance risks for my company and those of my recipients.
As a reminder, my attachment is now duplicated on 12 different servers, deliberately located in geographically distant areas (often different countries). I would like to know which countries these are, and how long my file will be stored there, to better understand the carbon footprint of my email. For example, using mail servers powered by renewable energy could significantly reduce their environmental impact and therefore the pollution from my emails.
On my side: the locations of the servers are not disclosed by my email provider Google. By paying an extra fee, I learn that I could, however, choose in which country the backup copies are stored… From a very short list, which only offers me Russia.
As for how long my attachment will be stored there, the answer is simple: it will be stored there indefinitely, for eternity, until my email account is completely deleted.
On the side of my recipients, I have no control: management is up to them, and is probably similar to what is imposed on me. On their side, my attachment will also be stored in various countries, in multiple copies, for eternity.
Solutions that make all the difference to an email’s carbon footprint
Faced with such absurdity and to escape the triangle of inaction that pushes us to wait for others to act, the solution for more responsible emails slowly becomes clear to me: store my file on my own cloud (Google Drive, OneDrive, etc.) and only send a link to my file by email, rather than the file itself.
This way I would keep much better control over my file: it will not be replicated on any server that I do not control. In addition, the recipients of my email will be able to view my file directly online, rather than downloading and storing it on their computer if that is not necessary. Yay!
However, I have no control over the geographic area where my Google Drive files are stored, and this method requires constant maintenance of my online space to manually delete obsolete files and stop the associated greenhouse gas emissions.
Fortunately, there is one last solution tailored very specifically to my need: file transfer services. You probably know at least one: WeTransfer, TransferNow, etc. – there are many solutions!
These file transfer services guarantee me time-limited storage: my file will be automatically deleted from the file transfer servers where it is stored after a given period (30 days for WeTransfer, for example).
All that remains is to find a file transfer solution that guarantees my files are stored in France, and I will finally be able to send my attachments with complete peace of mind!
That’s how I discovered FileVert: a 100% French file transfer solution (French design, file storage in France with French companies). In addition, FileVert guarantees me an energy-efficient solution, servers powered by low‑carbon electricity, a carbon footprint offset via the GoodPlanet Foundation, and a set of statistics that allow me to track the energy consumption of my sent files. Bingo!
With FileVert, I therefore go from around twenty copies stored for several years to direct transfers automatically deleted after a few days. All statistics combined, I estimate that on average I go from 20 to 5 copies, for a storage duration that goes from 5 years to 2 months… I therefore divide the time x copies impact of my attachments by… 121!
Summary of email pollution...
This article describes a typical email journey that does not take into account certain elements that may increase or decrease the number of times my attachment will be duplicated. For example, if all my recipients belong to the same company, it is likely that their email server will keep only one copy (excluding backups), regardless of the number of people it is addressed to. Conversely, if my inbox is synchronized with another cloud service (iCloud, Google Drive, etc.) as is the default on many devices, my email could be duplicated many additional times, and the associated email pollution as well.
In any case, the attachments in our emails (although generally small files) are subject to a perfectly absurd and outdated management system and massive use worldwide, generating an environmental impact (continuous greenhouse gas emissions) and governance issues that are truly worrying. It is therefore essential to adopt from today onwards solutions that address these issues, and to avoid a phenomenal waste that brings absolutely no benefit.
Frequently Asked Questions (FAQ)
What is the carbon footprint of an email?
According to Ademe, a simple email emits on average 4 grams of CO2, while an email with an attachment generates 35 grams of CO2, i.e. 7 times more. This difference is explained by the duplication and prolonged storage of attached files on multiple servers.
How much CO2 does an email contain?
An email does not “contain” CO2, but its sending, storage and processing generate greenhouse gas emissions. The carbon footprint varies from 4 g to 35 g of CO2 depending on the presence of attachments, with an uncertainty of 100% according to Ademe.
Which pollutes more, an email or a letter?
An email with an attachment (35 g CO2) pollutes more than a standard paper letter (around 20 g CO2). However, digital pollution mainly comes from prolonged storage: unlike a letter that exists in a single copy, an email can be duplicated up to 20 times on different servers.
What pollutes more, email or paper?
For a simple document, paper can be more polluting. But for attachments stored indefinitely across multiple data centers, digital easily exceeds the impact of paper. The key factors are the storage duration and the number of copies generated automatically.
Why do attachments pollute so much?
Attachments are automatically duplicated on many servers (backup, synchronization) and devices (computers, smartphones). A file sent to 3 people can exist in 20 different copies, stored for years in energy‑hungry data centers.
How can I reduce the carbon footprint of my emails?
Use file transfer solutions like FileVert instead of attachments, regularly delete your old emails, avoid unnecessary “reply all”, and favor links to cloud documents rather than attached files.
Are data centers really polluting?
Data centers account for around 4% of global greenhouse gas emissions. They consume considerable energy to operate and cool 24/7. That’s why choosing services that use renewable energy really makes a difference.
How can companies act on digital pollution?
Companies can raise employee awareness of best practices (as Eli does with its digital sobriety challenges), choose responsible providers, and implement policies for regular cleaning of inboxes and storage spaces.
Should we stop sending emails?
No, but we need to use them intelligently. The goal is not to eliminate digital communication, but to avoid waste: unnecessary storage, multiple copies, and attachments for temporary documents. Every action counts in the transition to more sustainable digital practices.
What is the impact of an email compared to other everyday actions?
An email with an attachment (35 g CO2) remains relatively low compared to a meal (2 kg CO2) or 10 km by car (2.1 kg CO2). However, with 375 billion emails sent daily worldwide, the cumulative impact becomes considerable. It’s the multiplication of small actions that matters: a French employee sends an average of 33 emails per day, i.e. potentially more than 1 kg of CO2 per day just from emails!