The Symantec Messaging Gateway virus definitions are out of date and/or you notice the logs are filled with definition validation errors between July 27 and July 29, 2013.
Error: The downloaded antivirus definitions could not be validated.
There was an issue with the certified virus definitions that caused validation errors for automatic scheduled updates. This issue began on July 27th and was resolved on July 28th. However, the error may persist in some circumstances until the virus definitions are manually reset by utilizing the Rapid Response virus definitions.
On most systems, the issue self corrected on July 28th. If the error is persisting beyond that date, change to Rapid Response definitions until the definitions are updated, then revert back to automatic cheduled definitions if desired.
Steps to change to Rapid Response definitions: