Everything Enterprise Vault client related used to be what I was 'all about' when I was working in Symantec Enterprise Vault Engineering. Okay I also dabbled with tons of other stuff, but I was somewhat of a subject matter expert when it came to things relating to the Outlook Add-in. That's partly why it irks me when I see things like this technote suggesting to perform the Outlook Add-in install by first of all disabling UAC. I mean a security firm should really recommend this, I don't think. Anyway, it is an interesting one, and it brings up the question that is often asked about why there is a setup.exe and an MSI file - it's all down to what 'regular' users can launch.
Take a look at the technote: http://www.symantec.com/docs/TECH209344
Would you disable UAC?