Stealthseminar's Email Reminders can be Enabled or Disabled at the Scheduling section in your webinar event (as shown below) a default message is setup to send when enabled.
Customizing them is an option; You can preview default messages in the Customize section. If you want to customize them there you can, article links how to are provided below.
Our system will send 3 default type reminder emails based on the Registrant's schedule choice:
Registration Confirmation Email
60-Minute Email Reminder
5-Minute Email Reminder