if (preg_match('/^(forum|orum|rum|um|m)?#([0-9]+)$/', strtolower($this->senderName), $matches)) {
            $dataProvider->query->joinWith(['message' => function ($q) use ($matches) {
                $q->joinWith(['sender' => function ($q) use ($matches) {
                    $q->andFilterWhere(['and',
                        [User::tableName() . '.id' => $matches[2]],