The basic mail module is one of the new core modules and let you add an email address field. The module is enabled by default.
The address fields can be displayed in different formats: e.g. as clickable link or as plain text.
You can add a field 'email' to a contenttype
You can set a default value if you want.
In 'Manage display' you can choose the display you want: plain text or a clickable link.