You can email the participants enrolled in an Event and select any History status. For example, you can email all enrolled users, or perhaps those that are canceled or "no show" after the Event.
1.Navigate to the Calendar.
2.Locate and click the Event on the Calendar.
3.Click the Users tab on the right side of the page.
4.Using the Search at the top of the page, filter the location, if relevant, and the History Status of those you want to email.
5.Click 
.
6.Click SELECT ALL.
7.Click the Email 
icon on the toolbar.
8.If appropriate, click the Template arrow to select an available message Template.
9.Enter or edit the message text and variables as required. You can include the [EventAttachments] variable at this point if required.
10.Click 
.