There are default email templates available for your convenience. You can see these under Settings > Email Templates.
Figure: Click Settings > Email Templates for All Templates
The default templates preset in your account are titled
Invoice Auto Reminder 1
Invoice Auto Reminder 2
Invoice Auto Reminder 3
Invoice Auto Reminder 4
Invoice Auto Reminder 5
Payment Received Notification
Send Estimate
Send Estimate Reminder
Send Invoice Reminder
Send Thank You Note for Payment
Figure: List of All Email Templates Available
By clicking on each template, you can edit it for your business needs.
Figure: Click on Email Template to Edit as Needed
The available account placeholders for each template are listed under the template itself, so feel free to edit as required