How can I give my images a round corner?

When you use our default email boilerplate, click at the image and choose the class Round Corner Img.

You might not see the round corners in the editor, but when you click at Test you will see them in the preview. 

The images will get a 10px border-radius. If you want a different border radius, you can overwrite the default value in Skins. Add this css code with your desired border-radius value under Scripts - Email - CSS

.myimageroundCornerImg, .roundCornerImg {border-radius:25px!important;}

You can add this code under account settings, when all projects should have the same value, your you choose your specific project and add it there.
Don't forget to refresh your email draft to see the changes.

Note that the corners will not be round in Outlook (Windows).