There are a couple of ways to prevent a lead that has registered from being sent a second invitation.
Perhaps the most straightforward method is to have a second smart campaign for sending the second invitation. It can be requested from the smart campaign for sending the first invitation. It would have the following filter in its smart list:
Filter 2 - Member of Program |
Member of Program is 'true' |
|
Program is 'Webinar' |
|
Progression Status is not 'Webinar > Registered' |