The primary or license contact email address is the only email that can be used to reset a forgotten administrator password, and the primary email for receiving communications from MSP. This is the email address that was originally specified when the license was purchased.
To see who this person is for your account, open a copy of MSP on your computer and click on the Licensing pane on the left side of the program window. This screen will show the current license contact, license contact email address, license contact phone, and billing email. Just click on the information to update it.
This information can also be accessed by logging in to your account. A separate billing contact can be entered in "billing settings" at the top of the account window. Reminders about maintenance expiration are sent to both the primary contact email and the billing contact email.