Hello dave-gas1982,
Welcome to the Community.
Syncing Gmail contacts made it possible in QuickBooks. Let me show you how to do:
- Click on the Plus icon and choose Invoice.
- In the Customer name drop-down, choose Add new.
- Click on Connect your Gmail account button.
- Log in your Gmail account.

For other email providers, you may want to check for a third party app that will sync email address to QuickBooks. Please go to https://apps.intuit.com and choose your region to view varieties of applications.
Let us know if you have more questions. Thanks!