This guide refers to developing Email Templates with HTML
Create a template
Email template is a .zip archive containing index.html in its root.
Please make sure that your index.html is UTF-8 encoded.
Actual message size after base64 encoding is limited to 10 MB per message, which means 6 MB limitation of raw message size.
The larger your email message is, the slower it's delivered and downloaded on the user's device. Large messages produce more system load and can trigger spam filtering. Moreover, some email clients clip large messages, and the recipient needs to click on "View entire message" to see the email message in full. Please take into account that emails you send should be as light as possible.
To ensure that various email clients render your email message properly, please consider inlining CSS. It provides more compatibility and guarantees correct performance of your email styles in email clients not supporting external and embedded styles. For example, embedded styles placed in the <head> of the HTML document are mostly stripped out by Gmail.
To embed images in your email template, use inline embedding (base64 images) or link out to images to load them from an external server.
Encode your image with a base64 tool and add a base64 encoded string to the HTML code as follows: