There is no Safe sender list (or Whitelist) "out of the box" in Gmail. Whatever further emails from a particular addressee do not end up in spam, there are several methods that we will describe below.
Mark it as Not Spam (if the email is already in spam).
Create a filter
Settingsbutton in the menu that appears.
Filters and blocked addressestab.
Create a new filterbutton.
Fromfield with the desired email. If you want to add all emails of the domain to the white list, type "@domain" (example: "@example.com") in the "From" field. Leave the rest of the fields empty (so that other possible rules will not apply to our filter).
Never send it to Spam
Filter created! To edit or delete a filter, use the
delete buttons on the filters
tab of the settings page. The pages of editing a filter are similar to those of creating it.