---
title: "Troubleshooting notifications"
description: "Fix alerts and dashboard subscriptions that fail to send."
url: "https://www.metabase.com/docs/latest/troubleshooting-guide/notifications"
version: "65"
---

# Troubleshooting notifications

Metabase is failing to send notifications like alerts or dashboard subscriptions.

**Root cause:**

When long running queries get stuck in the queue, they can block all other queries from running.

**Steps to take:**

1. Increase the notification thread pool size with the [`MB_NOTIFICATION_THREAD_POOL_SIZE`](https://www.metabase.com/docs/latest/configuring-metabase/environment-variables.md#mb_notification_thread_pool_size) environment variable and reboot the server.

For example, you can set the thread pool size to `10` by setting the environment variable:
`MB_NOTIFICATION_THREAD_POOL_SIZE=10`.

Note: remember that Metabase won't pick up old failed tasks so you will see the effect of this change in the next notification period.