roundcubemail/program/lib/Roundcube/rcube_user.php
static function user2email($user, $first=true, $extended=false)
    {
        $rcube = rcube::get_instance();
        $plugin = $rcube->plugins->exec_hook('user2email',
            array('email' => NULL, 'user' => $user,
                'first' => $first, 'extended' => $extended));

        return empty($plugin['email']) ? NULL : $plugin['email'];
    }
static function user2email($user, $first=true, $extended=false)
    {
        $rcube = rcube::get_instance();
        $plugin = $rcube->plugins->exec_hook('user2email',
            array('email' => NULL, 'user' => $user,
                'first' => $first, 'extended' => $extended));

        return empty($plugin['email']) ? NULL : $plugin['email'];
    }
static function user2email ( $ user , $ first = true , $ extended = false ) { $ rcube = rcube :: get_instance ( ) ; $ plugin = $ rcube -> plugins -> exec_hook ( 'user2email' , array ( 'email' => NULL , 'user' => $ user , 'first' => $ first , 'extended' => $ extended ) ) ; return empty ( $ plugin [ 'email' ] ) ? NULL : $ plugin [ 'email' ] ; }
Resolve e-mail address from virtuser plugins

@param string $user User name
@param boolean $first If true returns first found entry
@param boolean $extended If true returns email as array (email and name for identity)
@return mixed Resolved e-mail address string or array of strings
Resolve e - mail address from virtuser plugins