Images can grab your subscribers’ attention. With pictures, you can show them your latest product, the items on sales, and even the best-selling goods. But while images can hook your subscribers, they can also be the reason why your emails go into the Promotions tab.
So instead of cramming your emails with images, use them sparingly. One image with a small file size should be enough.
Plus, avoid using your business logo as your profile picture. Gmail may flag it as a Promotional email or spam.