Mark, your web browser probably isn’t configured to do anything in particular with mailto: links, so clicking them won’t do you any good (you can always right-click and choose “copy email address” and then paste it into whatever email you use).
If you use chrome and gmail, you can make chrome use gmail for mailto links by following these instructions:
https://blog.hubspot.com/marketing/set-gmail-as-browser-default-email-client-ht