FYI: I checked the behavior of the forum software. Mylittelforum also checks the email-address during the registration procedure. If the email is already used, an error is thrown, i.e.,
There is already a user with this e-mail address .
HOWEVER, if a user is registered, it is possible to change the email address. In this case, the new mail address is surprisingly not checked against existing ones. I will open a ticket because it is inconsistent.
applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences