IMail Anti-Virus Premium Edition uses Symantec's Scan Engine technology. It is designed for high volume and reliability. You can scan email from multiple copies of IMail Server. LiveUpdate allows virus signatures to be applied without interruption of virus scanning or email delivery.
IMail Anti-Virus Standard Edition uses Softwin's BitDefender technology. It scans email on the local machine only. If you have multiple copies of IMail Server you will need multiple copies of IMail Anti-Virus Standard Edition. Also, when virus signatures need to be updated, email delivery is paused, the updates are applied, and delivery is resumed.
With both products, the virus signature updates can be scheduled to happen automatically without user intervention. Both products integrate directly with IMail Server and are administered through the IMail Administrator and/or the Web Messaging interface.