Функции защиты от нежелательной почты: поиск [проверка] получателей и создание объединенного списка надежных адресов.

recipient lookup:

http://technet.microsoft.com/en-us/library/bb123891.aspx

One benefit of the Recipient Filter agent is the ability to verify that the recipients on an inbound message are in your organization before Exchange 2007 transmits the message into your organization.

safelist aggregation - это объединение в одну базу всяческих списков надежных получателей, надежных отправителей и т.д. от каждого пользователя:

http://technet.microsoft.com/en-us/library/bb125168.aspx

In Microsoft Exchange Server 2007, the term safelist aggregation refers to a set of anti-spam functionality that is shared across Microsoft Office Outlook and Exchange. This functionality collects data from the anti-spam Safe Recipients Lists or Safe Senders Lists and contact data that Outlook users configure and makes this data available to the anti-spam agents on the computer that has the Edge Transport server role installed.