With Alerts, Tableau sends you an email when a condition is fulfilled in your data after a refresh. For example, if you have a visualization with daily sales, you can configure an Alert to receive an email when the sales are above or below a certain amount. An Alert is a great way to allow you to do something other than check your data every day on Tableau Server. You can set an Alert on any visualization as long as it has an axis.

To create an Alert, click on the axis, then on the Alert button on the toolbar. A new window opens to configure the Alert, illustrated here: 

In this window, you can set the following:

• The Condition (Above, Above or equal to, Below, Below or equal to, or Equal to) and the Threshold to trigger the Alert. Tableau indicates to you whether the condition is currently true or not.
• The Subject of the email.
• The frequency of the emails (only the first time that the condition is true or Daily at most, for example).
• The Recipients of the email (you can specify multiple users who will receive the email).

Let's create an Alert on the Tourism View:

1. Click on the axis of the Income by Region visualization (it turns blue when selected).
2. Click on the Alert button.
3. Configure the Alert to send you an email with a subject of Tourism Income above 1,250B! when the value is equal to or above 1,250,000,000,000. If you didn't filter a specific Region, the condition is true for the year 2012. The configuration window should look like the preceding screenshot used to illustrated the Alert configuration window. 
4. Click on the Create Alert button.
5. Click on the Refresh button in the toolbar.

6. You should have received an email like this one, with a screenshot of the Alert:

As you can see, the Alert feature is very useful, probably as much as the next one: Subscribe!