Install using:   ciscoemailsecurity_7-#-#-###.exe -S

**Important note... I can't get this method to work via KACE.  When the install runs as the user "SYSTEM", the installer will error:  "Error: -3 The system cannot find the path specified."

I suggest putting a self-deleting script into the allusers startup folder or adding a runonce registry entry.  This way the script can launch the silent install as an actual user. 

My batch file in KACE:

REG ADD HKLM\Software\Microsoft\Windows\CurrentVersion\RunOnce /v IronPortPlugin /d "\"%~dp0CiscoEmailSecurity_7-1-1-002.exe\" -S" -F

You can extract the msi using:

 ciscoemailsecurity_7-#-#-###.exe /a

...however it's useless to try to get the MSI to install properly... at least in my various attempts