Recipient Filtering is a process where e-mail destined to addresses not hosted on your mail server are rejected during transmission. This is an important tool in reducing the volume of spam serviced by your mail server.

PerfectMail™ performs recipient filtering on incoming e-mail based on it's list of known e-mail addresses. Under normal operation, PerfectMail uses a progressive scheme that selectively queries your mail server to build a local database of known e-mail addresses.

To support this functionality, it is important that recipient filtering is enabled on your mail server. There are notes in the reference section for enabling this in Microsoft Exchange™ (which has this feature disabled by default.) If recipient filtering is disabled PerfectMail will receive responses that make it look like all e-mail addresses are valid on your mail server.

If recipient filtering cannot be enabled on your mail server, you need to disable this feature in PerfectMail's Domain Admin pages.