How green is your email marketing?


A while ago I saw a press release from an ESP claiming to be net zero. At the same time, I was actively taking an interest in all things green having taken on an electric car. This seems to be the net zero version of a gateway drug to becoming obsessed with all things green.

This company statement piqued my interest, but I was a little sceptical about the report and I couldn’t help but think this was greenwashing in action as it was light on the calculations.

You might think email is green. After all you don’t see big columns of toxic smoke billowing out of your ESP after a large send. And clearly compared to traditional direct marketing trees aren’t felled nor fuel consumed by the delivery vans shipping flyers all over the country.

But anything that uses energy has the potential for contributing to climate change. And just because email marketing isn’t anywhere near as bad as print mail, or say, the airline industry, we all need to do our bit to reach net zero. If we don’t make some minor compromises to help tackle climate change why should anyone else?

So, I thought I’d set out and try and work out how much carbon an email marketing campaign generates. It should be said that calculating the carbon footprint of this sort of thing is insanely difficult as it can depend on various factors such as the size of the email, the energy used to transmit and store it, and the method used to power the devices and infrastructure involved in the transmission.

We are also going to look at just the sending of marketing email not the creation of it, nor the processing of it by spam filters, or the consumption of goods bought on the back of the email promo, and definitely not on how the email marketer travelled to work or what they ate for breakfast!

The first port of call is to look at what research has been done on email. All studies seem to be based upon ‘normal’ email where the research put a lot of emphasis on the electricity used by a computer while composing the email, and the transmission and receipt of the email.

The problem with that is we might spend a fraction of the time per recipient composing the email. A short text email might be just 4KB but the HTML alone in a marketing email could be 100KB. Some of the studies look at if an attachment is used but marketers don’t generally send these – but they will include a lot of hosted images that if opened have a similar impact.

My suspicion is this ESP that claimed to be net zero is using the 4KB email size to justify their claim but for email marketing this clearly isn’t fit for purpose.

A better calculation would look at the energy used to:

  • Transmit the email from the ESP
  • Download the email to the recipient
  • If the email is opened, the energy used to fetch all of the images

This is closer to calculating the carbon cost of a web page so we can adapt this useful calculator from Chris Adams.

We need some numbers to plugin here, so I dipped into my promotions tab and roughly speaking a HTML of a marketing email is around 70KB on average. The images in the emails are around 1.5MB on average.

If we say our email is being sent to 1M people, and 30% of them open (including iOS 15 proxy opens), and we also assume the electricity used all along the way comes from the typical mix of coal, gas, nuclear & renewables etc) then we get the following from the calculator:

Sending the email:

70KB (0.07MB) email x 1M = 60.647 Kilos of CO2

Receiving the email (The same happens in reverse):

70KB (0.07MB) email x 1M = 60.647 Kilos of CO2

Downloading the images:

1.5MB x 300K opens = 298.902 Kilos of CO2

Total CO2 = 420.196 Kilos

Now if we say send 3 emails a week for 52 weeks a year that follow this pattern we get (156 emails x 298.902 = 46,628 Kilos per annum.

Is that a lot? Well, how does it compare to commonly known carbon emitting activities?

  • 23 passenger vehicles driven for one year
  • Approximately 11 homes' energy use for one year (USA average)
  • 58 long haul flights

Now my calculations aren’t perfect in anyway (this is not a scientific paper!) and I’m sure experts in this area would be able to pull them apart but hopefully it gives some sort of idea.

The next question is ‘what is the carbon footprint for the entire email marketing industry.’ This is also difficult because we don’t have a good handle on how many emails are sent each day. 300 billion a day is an often quoted figure for all emails – I’d have a guess that 10% of those are what we might classify as marketing emails.

If we take that and take our previous example to get an average amount of carbon per email over the course of the year this equates to 4.6M tonnes of CO2 for all email marketing activity (I won’t show all the working – there are too many zeroes to make it readable!).

  • 1.1 million cars driving for a year
  • Average energy consumption of over 500,000 homes
  • Over 1,000,000 long-haul flights
  • Annual carbon emissions of a small country such as Nepal or Iceland

Again, this isn’t really about how this compares to other industries or activities but if we take the view that we all have to do our bit what can we do as email marketers to lower their carbon footprint?

Send less email

The fastest way to reduce our impact on the environment as email marketers is to not send those emails we know aren’t going to be opened. We could all probably trim 20% of our lists overnight without noticing the impact on the bottom line even before we think about the deliverability benefits it can bring.

Refine content

Ironically the ESP that claims they are net zero seems to have the largest emails as their drag and drop editor creates huge, bloated HTML. Keeping our code clean, and resizing images so they are no larger than they need to be, also improves load time for those on bad mobile connections.

Ensure your ESP is green

If all the electricity produced in the world came from wind turbines and solar panels rather than burning coal and gas then there wouldn’t be an issue. So, working with an ESP who hosts with a data centre powered by a higher mix of green electric also brings the carbon down. What you aren’t in control of though is the electricity consumed by those downloading your email and images.

The impact Apple MPP has on the planet…

And one final point that I hinted on earlier. The iOS 15 fetching of emails has had the unintended consequence of creating more carbon. If we use the rule of thumb that this Apple update has doubled the normal amount of opens then in the annual total 1.65M tonnes of CO2, or around 35% of all carbon emissions from email marketing is thanks to Apple and MPP. Thanks Apple.

Is email marketing green?

I’m not going to answer that as I think it is subjective. I don’t know who is the arbitrator of such things, and if you ask 2 different people I’m sure you’ll get opposing views. Let’s be clear though, it is not a carbon neutral industry yet.

But as an industry if we are to reach that point then a good starting point right now is to at least have some idea what our overall impact is.

jason blackeye s1w1SguZTI unsplash 600Photo by Jason Blackeye on Unsplash