The Spamhaus Whitelist is a realtime database of IP addresses and domains which have passed security checks and whose owners/operators agree to the strict terms of the Spamhaus Whitelist program. It allows internet mail servers to separate incoming email traffic into 3 categories: Good, Bad and Unknown, allowing mail server operators to block known bad email traffic, let known good email traffic pass safely, and heavily filter unknown email sources.
Intended for mail from qualified corporations, banks, accounting firms, law firms, airlines, medical centers, government agencies, and transactional mail from automated billing systems, ecommerce servers, online banking and booking systems, the Spamhaus Whitelist is designed to enable special and priority handling by mail servers of important mail from senders who are known to be extremely unlikely to ever send spam.
For email recipients, the Spamhaus Whitelist means a reduction in messages marked in error as spam by scoring systems and content filters. For email senders, it means an end to important mail lost in junk folders, delayed or wrongly tagged as spam.
For mail server administrators with high incoming spam levels it means you can use heavier, more in-depth filters without risking false positives from known good senders.
Only verified legitimate senders with clean reputations are approved for whitelisting and there are strict terms to keeping a whitelist account. Bulk email for marketing purposes is not allowed in any form and whitelist account holders must personally know or employ each sender that uses a whitelisted resource. This means that servers of ESPs and ISPs are not elegible for whitelisting, but servers of banks, airlines and private organizations are.
The IP Address whitelist, the SWL, is designed to contain both IPv4 and IPv6 addresses. Although initially it will contain predominantly IPv4 addresses, it's future primary intended usage is to enable networks to implement IPv6 mail services with control over IPv6 spam.
The Domain element of the whitelist, the DWL, enables automatic certification of domains with DKIM signatures.
Software controls ensure it is not possible to whitelist an IP address or domain that is on a Spamhaus Project blacklist, therefore the Spamhaus Whitelist can not be used to circumvent Spamhaus Project blacklists. A whitelisted source which later becomes blacklisted by Spamhaus Project is automatically suspended from the whitelist until the blacklisting issue is fully resolved with Spamhaus Project.