Hello, is there any way to block the possibility of creating several accounts for one e-mail address?
Hi, there’s no built-in feature for this (only the id is unique in XWiki) but you could write an Event Listener to offer that feature. It requires some technical skills though. Another option is to use the email as the id.
You could create a jira issue at XWiki Platform - XWiki.org JIRA to record the need (but someone will need to want to implement it, you could also sponsor the feature if you really need it, see https://dev.xwiki.org/xwiki/bin/view/Community/Contributing#HSponsoraFeatureorBug
Thanks