Recently I started my internship on the Productivity and Collaboration team here at Concurrency! One of the tasks I was given in my first couple weeks was to figure out how to make a clickable image on a modern SharePoint page that when selected, would open a new email message in the user’s default email application.
I found that using a Markdown web part was the easiest way to be able to manipulate the image to make it clickable. While you can add a link to an image web part in SharePoint, you can’t use the mailto: protocol, which I used to launch a new email window.
After creating a new Markdown web part, you can insert an image by using the following syntax:

Within the parentheses you can either provide a URL to an image file, or you can provide the relative path to the image if it resides within a SharePoint library.
At this point your chosen image is displayed. To open a new email by clicking the image, I used the “mailto:” Uniform Resource Identifier within the Markdown web part. To link it to the image, you need to change the syntax slightly:

Using this syntax, you will be able to successfully open a new, blank email by clicking on the image.