Email links are used to open an email client to start a new email message. The value you enter in the Link field must begin with mailto: and ends with an email address. For example: mailto:firstname.lastname@example.org
You can also add an email link by selecting Insert > Email Link, and then filling out the resulting dialog:
If you select the text you want to turn into an email link before selecting Insert > Email Link then that text will show up in the Email Link dialog. Otherwise, you must type in the text in the dialog box and Dreamweaver will add it to the page at the point where the cursor is.