yahoo

Yahoo has a complicated filtering setup that uses a variety of techniques to protect their users from unwanted email. They use a combination of rate-limiting and temp failing along with bulk foldering as defenses. Yahoo also uses some lists provided by Spamhaus including the PBL, SBL, and XBL.

Yahoo provides whitelisting and FBL services. For senders and ESPs to qualify for the Yahoo FBL they must sign their mail with Domain Keys or DKIM. ISPs are eligible for an IP based FBL. Whitelisting is available to senders who fill out an application and qualify.