Follow These Instructions for Gmail:
1. In your inbox, find an email from firstname.lastname@example.org (ex. your welcome mail for the free resource that you requested from us).
2. Drag this email to the “primary” tab of your inbox.
3. You’ll see that our future emails will go to your primary folder from now on.
For other email service providers (Yahoo, AOL, etc.) just add us as a contact in your address book. Additional instructions can be found here.