To create a whitelist to ensure that emails from a particular sender do not go to Junk:
- Add the contact to the Postbox Address Book or Contacts.app (if you're on macOS).
- Navigate to Preferences or Options > Accounts > [your account] > Junk Settings and then:
- Select the checkbox for Enable adaptive junk mail controls for this account
- Select the checkbox for Move new junk messages to, then select Other and navigate to your Junk or Spam folder for the account. For details on which folder to select, please see Mapping Folders.
- Under Do not automatically mark mail as junk if the sender is in, select the checkbox for the address book the contact was added to.