Not sure about what would cause it in 10.6, but we don't support 10.7... so anything that doesn't work there wouldn't be a surprise.
Also, SEP for Mac doesn't have the email plug-ins, so if we're interferring with the email, it's because of Auto-Protect. You could make an exception for the email folders (not recommended as a permanent fix) and see if it changes behavior.
As for Outlook 2011, I'm sure they do things different from Outlook 2007 and some adjustments may not be seen until RU7.