Why Gmail Clips Emails
The main reason it happens is file size. If the HTML code that makes up your email is too large (usually around 102KB or more), Gmail will trim it.
Your email’s HTML size isn’t the same as the visible text and images you see. It also includes all the underlying code, tracking and formatting. Even a simple-looking email can grow in size if it has a lot of formatting or many images.
Another, less common reason is special characters (such as © or é) that aren’t encoded properly. These can also cause Gmail to clip your message.