The WYSIWYG editor does not have a button for creating an email link but you can create one just like you create any other type of external hyperlink.

Highlight what you want to become a link (preferably the person's name or their full email spelled out).
Choose the hyperlink button from the WYSIWYG editor
Choose "External Link" since you're not linking to an asset in Cascade (another page, image or PDF).




In the "Link" field enter mailto: followed by the email address.
Add a title to describe the link.
Choose the Insert button.
Choose Submit.