In order to send an email alert within Salesforce workflow, we will first need to create an email template using the following steps:

1. Click on the setup gear icon in the top right-hand corner of the main Home page, as shown in the following screenshot:

2. Click on Setup, as shown in the following screenshot:

3. Navigate to the new email template creation page as follows: Email | Email Templates.
4. Select the Unfiled Public Email Templates folder.
5. Click the New Template button, as shown in the following screenshot:

We will be presented with the Step 1. Email Template: New Template page.

6. Choose the Text option and click on Next.

We will be presented with the Step 2. Text Email Template: New Template page.

7. Choose or ensure the Folder option Unfiled Public Email Templates is selected.
8. Check the Available For Use checkbox.
9. Enter Alert Opportunity Close Date in the Email Template Name field.
10. Accept the default Alert_Opportunity_Close_Date text that is automatically set in the Template Unique Name field.
11. Optionally, enter a description in the Description field.
12. Enter Alert Opportunity Close Date in the Subject field.
13. Paste or enter the following text in the Email Body field:

{!Today}

 Dear {!User.FirstName},

 The close date for the opportunity, {!Opportunity.Name} for the
 account {!Opportunity.Account.Name} is due within 21 days.

 Sincerely

 Salesforce System Administrator

14. Click on Save, as shown in the following screenshot: