Most email clients set limits to the size of emails' HTML code. For Gmail, it is 102Kb.
I.e., when your email size exceeds this volume, Gmail automatically "clips" your email.
How to avoid it?
Please reduce your email weight by removing some content in the containers, structures, and stripes and also minimize the number of styles applied to email elements.
For instance, the "Support for Outlook" option alone is 1KB per button in the email. Disable this option to prevent your emails from being clipped.
Also, you can export the email template as an HTML:
Toggle the "Minimize HTML" button; this will reduce the weight of the email template file.
Then open this file with any text editor and copy/paste the HTML code into the service you need for further sending to Gmail.
Following this link, you can find more information on how to test emails.
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