The Messaging Security Agent uses the following sequence to scan email messages:
Scans for spam (Anti-spam)
Compares the email to the Administrator’s Approved/Blocked Senders list
Checks for phishing occurrences
Compares the email with the Trend Micro supplied exception list
Compares the email with the Spam signature database
Applies heuristic scanning rules
Scans for content filtering rule violations
Scans for attachments that exceed user defined parameters
Scans for virus/malware (Antivirus)
Scans for malicious URLs