unable to set mailing list as contact address

We'd like to set <email address hidden> as the contact address for the ~ubuntu-doc team because it is annoying that all team members receive individual emails through the "Contact this team" button on Launchpad. The way to contact the team is by posting to the mailing list. However when trying, I get this error:

<email address hidden> is already registered in Launchpad and is associated with Registry Administrators.