Graphic embedded in auto-reply email fails to display in Gmail

I have re-added this JPG graphic multiple times into the JF email editor.

Sometimes it displays correctly when that email is sent to a Gmail address. Sometimes (most of the time) it does not.

Why aren't JF graphics being reliably displayed?

Greetings,

I've added the image in your email again and sent a test submission on your form. I've received the image correctly:

Should you need further assistance then please let us know.

Thanks