Img to CSS convert images to html/css. Email clients won’t block html/css images, so you can be sure that your audience will see your image.
This is great news for people who want to include logos in their emails, but don’t want to sacrifice the user experience with a “click here to enable images” banner.
Unfortunately, the resulting html/css is rather large, so only small images can be converted. Large images will still convert, but may cause the email client to clip the email. This does have the benefit of making the tool unattractive to spammers who make up for their low click-through rates by sending tons of emails.
Creating an Img to CSS paid account gets you access to an API, the ability to flatten transparent PNGs with a custom background color, and priority support.