Google Message Security for Google Apps Administration Guide - Manual (Page 181)

Spam Filters 181
Messages are held in the Early-Detection Quarantine for 8 hours to allow time for
virus-definition files to be updated, and then those messages are scanned again
for viruses based on the updated definitions. Those messages are then disposed
of according to your Virus Blocking settings.
Administrators and users who have access to the Pending tab in Message Center
can see messages in the Early-Detection Quarantine.
Outbound Spam Scanning
Outbound Spam Scanning is designed to improve the deliverability of messages,
address the misconfiguration of mail servers as open relays, and block internal
senders of spam.
From time to time, an open relay transmitting mail through the Postini servers
causes the Postini servers to be associated with spammy behavior, which then
results in blocking all mail from the offending domain.
There may also be occasions where someone in your organization is sending
spam, or when computers on your network are infected as part of a botnet.
With Outbound Spam Scanning, messages are evaluated on an individual basis
according to content: valid messages are transmitted normally, and offending
messages are bounced (with a 500 reply code).
Outbound messages are evaluated by the following sequence of filters:
1. Outbound Virus Blocking
2. Outbound Content Manager
3. Outbound Spam Scanning
4. Outbound Attachment Manager
These filters operate somewhat differently than Inbound filters. With Inbound
filters, if a message is approved by Content Manager, then it bypasses the Spam
Filters regardless of spammy content. With Outbound filters, even if a message is
approved by Content Manager, it is still scanned for spammy content by Outbound
Spam Scanning.
There are no controls in the Administration Console with which you can configure
Outbound Spam Scanning. Configuration is handled by Postini administrators. If
you see an undue number of bounce messages, contact Postini Customer Care to
discuss your options.
The number of messages caught by Outbound Spam Scanning is reflected in
Outbound reports that include the number and percentage of bounced messages.