When we talk about the size of an email, we refer to three main aspects:
- the size of the HTML file sent-that is, the structure and content of the HTML version of the email
- the size of the external objects-primarily the images
- the overall weight, i.e. the “sum” of all the elements that make up the email and determine its loading time.
Heavy emails take longer to fully view, this can be a problem considering that more than half of users tend to trash an email within two seconds of opening it.
The email layout may not work without the accompanying images, particularly if the headlines are not handled as text, the email message then may be incomprehensible, compromising the user experience.
It is important to keep all these files small, but what is the maximum size and what should we aim for?
The HTML Code
Excluding plain text messages where not even a boldface is allowed, the body of an email is nothing more than a web page in an HTML language.
Unfortunately for insiders, with a 20-year-old syntax. Nested tables define the layout, CSS styles flesh out text and objects, images are typically referred to as external resources, and downloaded by the email client only upon opening* .
The maximum recommended size for HTML alone is 100 KB, going beyond that means running into some deliverability or layout problem. For example, Gmail truncates HTML to 102 KB, hiding the final part of the email and potentially breaking its layout.
If your tracking pixel is at the bottom of the HTML it will not load, also affecting open statistics. Most commercial emails can safely stay within 50 KB, unless articulated layouts are to be represented or numerous blocks are included for very long content.
A few sensible tricks to reduce the size of HTML
- Keep code clean: nothing is ever thrown away, but an email is not the ideal place to keep older versions of blocks and layouts.
- Don't overdo it: good code is lean and clean; choose an effective way to represent the layout without using 30 nested tables.
- Take advantage of CSS: some styles will necessarily have to be inline, but move as much as you can into CSS to reduce the overall code.
- Simplify your design: avoid unnecessarily complex layouts that require a lot of code to handle. Single-column layouts have the double benefit of being simple and naturally responsive, without requiring a second representation for mobile.
- Avoid embedded images and attachments: don't embed images and replace attachments with a link inside the email for downloading.
Images and other assets
The elements external to the image, downloaded at opening, are the images, any external CSS files or custom fonts attached.
Most images can be contained within 100-200 KB, except for high-resolution images served for retina displays that are double the size in pixels, or animated GIFs based on the number of frames.
Choose the most suitable size and format for the images, depending on the size in px and the type of content (logo, graphics, photos, ..).
The overall payoff
HTML, linked images and other assets combine to determine the overall weight of the email.
We recommend not to exceed 200 KB or in rare cases 500 KB total, it will allow your contacts not to have too much latency in opening the email.
In fact, the loading time of the email will depend on the total weight, combined with the speed of your Internet connection. In addition to this, the speed of response of the server hosting the images will help determine the overall open time.
A good expedient may be to set up a simple layout, where the texts still allow for the narrative of an email even without the uploaded images. In this email the headlines, CTA and descriptions are in text format, making the message more than understandable. For images, we have set a meaningful “ALT” alternative text.
How does magnews help you?
With the Size Control feature, you can understand in detail what is weighing down your communication.
Before sending, from the communication home page, use the Message Size Check link.
A detail window opens.
Size of sent message = size in KB that the email has, i.e., HTML version + TXT version + any attachments and embedded images.
Size perceived by the contact = data that the contact needs to download in order to properly view the email in their email client.
HTML version + TXT version + any images + style sheets + custom fonts.
The carbon footprint of an email
A final assessment of the weight of email with an environmental impact perspective.
Transmitting, processing, reading and storing a 1 MB email has a carbon footprint that recent studies have measured at 4 g. of CO2. There is no serious impediment to crafting email messages with clean, reduced HTML and optimized images.
An email signature, such as through DKIM, can finally reduce mail providers' anti-spam checks on incoming messages.