Hi Lisa,
You can create a custom email in your event under Email > Event Emails > Create Email. You can add your own content and text to create a custom Thank You email.
If you marked participation and only want the email to go out to those who attended the event, you can change the audience type to "Attended Registrants". If you didn't mark participation, you can change the audience type to "Accepted Registrants".
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Megan Burns
Customer Success Manager
Cvent
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