Manual:$wgEmailAuthentication

Details
Set to  to enable email authentication: all email functions (except requesting a password reminder email) only work for authenticated (confirmed) email addresses. On account creation or when users change their passwords or on request, a confirmation token (link) with a limited life time is mailed to that unconfirmed email address.

When the user returns with that token to the wiki, the email address is confirmed.

The confirmation status ("") is always shown in the user email preferences.

It also enables the other email notification options.

If set to  then the email notification options work without having to authenticate (confirm) email addresses.