Whitelisted

He may never be entirely successful, but the difference in being "blacklisted," "greylisted," "bluelisted" or "whitelisted" is considerable.

[…] to accelerate the flag’s attempts to become ‘whitelisted’ at IMO […]

[…] is the only client-side antispam tool that quarantines any incoming mail that doesn't come from a whitelisted sender.

This means that many spam senders will never become whitelisted and email will never be accepted from them.

One way is to create whitelist email addresses, a special email address that can be given to senders who are not yet whitelisted.

Hotmail utilises this scheme and is the only method of becoming whitelisted with Hotmail.

Otherwise, traffic going to another domain is blocked. the extension allows a way to add whitelisted sites, such that traffic from x.com is allowed to retrieve content from y.com.