Hi there, @sebastianvangreunen… a few things here… first, it is likely that the default privacy rule on the User data type is stopping what you are showing from working. Second, Bubble automatically checks to see if an email address is already in use in your system, so you don’t necessarily have to do that check. Finally, if you want to do the check so you can show your own error message, you can either modify your privacy rules to allow the check to happen or you can set up a workflow that catches Bubble’s duplicate email error and then show a custom message (you can search the forum for more info on how to do the latter).
Hope this helps.
Best…
Mike