Test and document how to configure multiple recipients for email notifications.

Apparently neither of the following seems to be working, so we have to find a way how to have more than one address there:

<AdminEmailAdress>
    foo@bar.xy,
    loo@top.xz
</AdminEmailAdress>

<AdminEmailAdress>
    foo@bar.xy;
    loo@top.xz
</AdminEmailAdress>