Extension:LookupUser

The LookupUser extension allows to retrieve information about a user such as email address, user ID and the user preferences, i.e. everything that the user has specified in their preferences.

This extension also displays the last time a user either made a login, or any edit, which it lists as the "User record last touched:" time and date element of its log (This will be displayed as UTC even if you've set a custom time zone/the server's time zone is different).

Usage
The extension is accessed via the "Special:LookupUser" page.