Microsoft Exchange 2007 and upwards does offer email archiving tools for business.  It can do this by the use of managed folders and storage quotas to make it work.

This can be configured to keep emails for up to five years in specific managed folders and used with inbuilt storage utilities and transport rules to make it all work.  Companies with a large infrastructure and in house Exchange engineers will be able to pull it off, but the average firm, with average support staff will be unlikely to.  If you know your hub transport from your rules engine then you stand a chance, if you don't then good luck.  I don't think Microsoft sets out to make everything it sells incredibly complicated, but it succeeds very well.

To my mind it makes for much easier mail archiving to pay someone to take care of it for me.  I can then have a flexible, scalable solution that grows as I grow and moves as I move.  With no upfront costs and no maintenance or licensing issues to contend with I can concentrate of my own business.

In essence, I could absolve myself of all responsibility for maintaining the product and pass it to someone like Archive Compliance.  I can let them take care of everything for me, confident in the knowledge that I'm covered when I need to be.

Hosted applications allow customers to concentrate on their business without the unwanted distractions technology can provide.