Content Scanning identifies spam based on the content of the message rather than the originating IP. The Messaging Security Agent uses the Trend Micro anti-spam engine and spam pattern files to screen each email message for spam before delivering it to the Information Store. The Microsoft Exchange server will not process rejected spam mail and the messages do not end up in the user’s mailboxes.
Note:
Do not confuse Content Scanning (anti-spam based on signatures and heuristics) with Content Filtering (email scanning and blocking based on categorized keywords). See Content Filtering.