Whitelist

Now referred to in the industry as an allowlist or a passlist, a whitelist is a system used to allow only certain senders or messages to pass through a filter. All other senders or messages are blocked.

The method of email filtering used to ensure that only emails from known and trusted sources are allowed is called whitelisting or allowlisting. It involves creating a list of approved or whitelisted senders and blocking emails from any other sources.