One or more users in your environment are receiving email messages containing the subject line with the phrase [warning - not virus scanned].
Examination of the message audit log shows a verdict of 'none' with an action of 'Deliver Message Normally' when searching for messages that meet the criteria of having phrase [warning - not virus scanned] in the subject line.
This message was sent to the Symantec Messaging Gateway software with the Subject line already modified. Symantec Messaging Gateway scanned the message and did not find any viral activity.
The software is functioning as designed and is not causing the alteration of the Subject line.