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## The Trend Micro Virus Scan Engine

At the heart of all Trend Micro antivirus products lies a proprietary scan engine. This engine has a long history in the industry and has proven to be one of the fastest.
The ScanMail scan engine is designed to work closely with the Virus Scanning Application Programming Interface (VSAPI) 2.6 and 2.5 available from Microsoft Exchange.

- VSAPI provides a virus-scanning implementation with high performance so that scanning occurs before a client can access a message or attachment. This low-level access facilitates the elimination of viruses/malware that file-level scanners cannot eliminate.
- VSAPI enables message scanning once before delivery, rather than multiple times as determined by the number of intended recipients, reducing processing time. This single-instance scanning also prevents re-scanning when a user copies a message.

The scan engine provides:

- Real-time multi-threaded scanning
  ScanMail performs all scanning in memory and is capable of processing multiple scan requests. When it receives multiple scan requests, it prioritizes and queues the requests that it cannot run immediately and runs the requests when resources become available. When a manual or scheduled scan is running and a client attempts to access an email message, ScanMail performs an immediate real-time scan on the requested message.
  ScanMail supports SMTP real time email message scans.
- Non-redundant scanning
  When ScanMail completes a scan of a message, it logs the message as scanned. If you access the message again, ScanMail checks to see if it has already scanned the message and does not scan the message a second time.