Hi everyone!
Update since problem solved on my side 
The problem:
I was trying to send an image through one of the variables but was using :encoded_in_base_64 in the variable instead of a plain URL. And so the image was sent to SendGrid as a long chain of characters, which then exceeded the 10000 bytes.
The solution:
@copilot has been really helpful and reactive in dealing with this issue so thanks and 
thumbs up to the team 
“When sending images, you should likely have a
tag in your HTML email template and have it’s “src” tag be a variable like %VAR1%. You could pass the link to an image to that variable so that its injected into the template properly and you don’t Base64-encode anything.”
So the trick is to normally input the file URL in the given variable in Bubble and to add a HTML code block in your SendGrid template that will call this variable.
- You could simply put
<img src="%VAR1%">in your HTML block alt="(image bloquée)"is for alternative text (when the image isn’t displayed properly)align="middle"is probably useless (if you only have your variable in that HTML)<center></center>is to have the image centered in you template. You could also use “right” / “left” / “top” / “bottom”
There’s also a conversation here on the forum.