Two large messages sent at the same time to Symantec Messaging Gateway (SMG) to different recipients could experience content mixing between the two messages under certain exceptional circumstances, including delivery to an incorrect set of recipients.
This issue is caused by rare collision of temporary filenames due to heavy load and backed up message processing queues.
This issue has been addressed with the SMG 9.5.4 release. It is recommended to keep up to date with the most current software build to access the latest bug fixes and security updates.
Messages involved are larger than 512KB.