Items will land in the Failed mails folder when the engine fails to initialize.Definitions in the engine are corrupt and not allowing auto-updates to complete successfully.Symptoms that the Kaspersky antivirus engine has become corrupt and cannot be initialized include: This article describes how to manually update the Kaspersky Virus Scanning Engine for instances when the automatic updates are unsuccessful or failing.
You can acquire a license for Kaspersky Virus Scanning Engine as it is not shipped with MailEssentials. GFI MailEssential uses multiple antivirus engines to scan inbound, outbound and internal emails for the presence of viruses.