Users are accustomed to documents being put into a document management system (DMS), so that others will be able to see the document. That’s the sort of application for which these systems have been designed.
But when it comes to putting their email into a corporate archive, some users freak out. Suddenly, their email contains a lot of highly personal material. They’re right. Much of email is very confidential in nature. Privacy is very important; access to others should only be on a selected basis, and according to a policy that’s understandable by everyone.
Hence the importance of finely grained access controls for archived email.