The Calendar event email invitation is sent to a contacts default email address.  

If a contact has more than 1 email address you will need to select the email address that is to be the default email address for your contact.  

To setup a default email address for a contact with more than one email address please see the steps below:

1. If a contact in your CRM account has more than one email address such as the example shown below you can select which email address is the default email for use when sending the contact e-Marketing campaigns or calendar event email reminders.

2. Open up the contact record and click on Edit as shown below in red to open up the contact details:

3. The email addresses are shown depending on which one is to be the default email address for the contact you will see a round button which you can select by clicking your mouse in the round circle - as shown below in red the circle is blank:

4. If you wish to make one of the email addresses the default email address then just click inside the circle as shown below:

5. Click on Update to save your default selection.

6. Now when you want to set up a calendar event email invitation to a contact it will select their default email address for the invite to be sent to as shown below in red:

7. Select the contacts email address and click on Save for the calendar invitation email to be sent to your contacts default email address.