Manual:$wgEmailAuthentication

Details
Set to true to enable e-mail authentication: all e-mail functions (except requesting a password reminder e-mail) do only work for authenticated (confirmed) e-mail 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 e-mail address.

When the user returns with that token to the wiki, the e-mail address is confirmed.

The confirmation status ("Your e-mail address was authenticated on ") is always shown in the user e-mail preferences.

It also enables the other e-mail notification options.

If set to false then no e-mail notifications are enabled for the entire wiki.