You can create Triggered Emails for Participants. The email is triggered to fire off of their Birthdate or their Participant Created On Date, as a celebration. For example, you can set up an Email Message to be fired on their Birthday. If the Participant doesn't have an email address, it will be sent to the Account holder.
This type of Triggered Email is system wide -- it does not need to be assigned to anything. You can have multiple of this type of Triggered Email in your database.
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 Participant , 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 Account, the Participant and the Participant's Orders, and then input that data into the email. 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, and choose the date range that the Triggered Email will be used. 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 Participant Birthdate or their Participant Created On Date. Input a day value, indicate before or after, and then select the type of date.
For example, you can send an email to the Participant on their Birthdate, as seen in the screenshot below. 