When using the built in email marketing tools for ZenSales you will have the option to send one of two types of emails.
One-Off emails are emails that you want to send ONCE to a customer or group of customers without changing the content. This would include marketing communications, newsletters, flash sales, and updates to your store or business.
On going emails are any emails you send regularly to customers that you would like to automate. It's important to note that while the content of the email is customizable, the overall message will remain the same to all customers. So if you would like to customize your tracking email or send a product follow up email then you would use this option for email.