You can create Triggered Emails for Products Purchased. They are sent to the Account holders who purchased the Product. The email can be triggered to fire off of the Order Date, or the Start and End Dates of Events in the Order. You can choose to only send the email when there is an unpaid balance. For example, you can set up an Email Message to be fired after five days when there is an unpaid balance on the Order.
This type of Triggered Email is assigned to a Product or a Category. You can have multiple Triggered Emails of this type in your System, and can assign multiple to any one Product.
Creating the Email Message
Login to the Administrative side of your database, and navigate to Settings --> Assignments --> Email Messages. Click to Add New Email. Input a Title, choose the type Triggered Product Purchased, and click the "Save" button.
You can now begin to compose your Email Message. Input a Subject, and add text to the Body. You can use plain text, and you can use Operators. Operators read data from the system that is relevant to the Order, Account, or Product, and input that data into the email. For example, if you are creating a message about the date, time, and location of the Event, then you can use then you can use the Product Start Date, Product Start Time, and Location City Operators. After you are finished composing your email message, click the "Save" button.
Creating the Triggered Email
Navigate to Settings --> Assignments --> Triggered Emails. Click the "Add New Triggered Email" button. 
Input a Title, choose the Type, select your Message, choose the date range that the Triggered Email will be used, and choose what will trigger the sending of the Email Message. If you want the Triggered Email to not expire, you can select No End Date.
The trigger is fired off of a date. The types of dates available are Product Purchased Date; Product Start Date, or Product Start Date. The Product Start Date and Product Start Date are the Event Start and End Dates Input a day value, indicate before or after, and then select the type of date.
For example, you can send an email to Account holder 30 Days prior to the event, as seen in the screenshot below.
You can choose to only send the email if there is an Unpaid Balance by selecting the "Only send if there is a balance remaining" checkbox.
Like with other Assignable Items, click to edit the Category, Region, or Product, go to Assignments, select the Email Tab, choose Triggered Emails, and drag the item from the Unassigned to the Assigned column.
For more information on assigning items, see the Product Assignment Video, or the Categories and Regions help files.