Internet Service Providers (ISP's) like Gmail and Microsoft will do all sorts of things to large or "heavy" emails when they receive them. You may have seen this on your mobile phone when the email isn't completely downloaded.
Topics covered in this article:
When an email client receives your HTML email there's a two-step process for rendering that email. First, the HTML is downloaded and rendered. Second, the images in the email are downloaded. This is why you will typically see the email load in two phases: HTML first, images second. The total size of the HTML and images combined plays into how fast the email will be processed by the email client both on desktop and especially on mobile devices.
Generally speaking, we recommend that you keep the size of your email HTML code to 125K or less. Individual image sizes should be kept to around 40K. If you have a large mobile audience, the smaller the total email size, the better.
In addition to helping your email load time, there are a few reasons why it is important to keep the total size of your email as low as possible.
Many email clients (especially mobile) truncate the email, cutting it off halfway or 3/4's of the way through. You will see a “Download More” button in many cases.
Example of message clipping…
ISP’s may block or "hold" large HTML emails for further examination. Large emails can be a sign of spam or an email carrying a virus or malware.
Example of a bounce back message indicating email is too large…
"Exceeded maximum inbound message size"
Mobile load time
With mobile opens between 60-70% of many email marketers email client stats it is even more important that your marketing email is as light as possible. Large images will slow down an email loading on mobile devices, especially if the device is not connected to wifi. The easiest way to see if this can be an issue is by testing your email load on a mobile device.
We've put together some tips for managing the size of your email. These tips will help improve user experience, engagement and deliverability.
Create lighter emails using emails with fewer columns, concise text content and more links off to your website for additional information. Use the right image format (more details below) and reduce the number and overall weight of images as much as possible.
When choosing your image formats, consider your options. The three most common formats are GIF, JPG, and PNG:
-Great for small, low color images, as well as images that include text
-Examples include logos and buttons, also animated images
-Great for photos (especially ones with lots of color) and making smaller file sizes
-Reduce 40% quality
-Examples include hero images
-Great for small images with transparency
-Displays best on mobile
-Examples include header images, logos, and images with text
You can find the size of your email in most email clients relatively easily. We’ve put together some notes for finding the size in Outlook and Gmail to help you get started!
Total email size (code + images)
Here's how to find the total weight - code + images - of your email using a browser:
1. Load the 'view email as webpage' link from your email in Chrome
2. Right-click on the email and select 'Inspect'
3. Select the Network tab from the inspector tools
4. Reload the email in the browser tab
5. The total weight in KB will appear at the bottom of the Network information
Email code size in Outlook
Open the email you wish to view the size for by double clicking on it so that it opens in a separate window. Then click File on the top left corner, and then click Info. You will see a button titled Properties on the right and the heading "Size" under it. This is the size of your email code, excluding images.
Email code size in Gmail
Using the search bar in Gmail, type in the email size. For example, “size:125k”…