There is a method of expanding existing storage using 'stubs'.  The body of the message is replaced by a hyperlink which drastically reduces its size.  There are third party suppliers who vaunt this as the ultimate solution to an organizations exchange storage problems.  A storage server is bolted on to the exchange and interfaced with it.  Backup software then runs in tandem with exchange and archives mails by replacing the body text with a link to the record on the storage server.  These links are called stubs.  It sounds a great idea in principle.  Mailbox volumes will be drastically reduced which means more can be stored on the existing storage.

This isn't without its own issues though.  Having a hyperlink in the body text of an email will mess up Outlook or Windows search.  There simply isn't enough text available to do a proper search.  As a heavy Outlook user myself, I live by my search option, and would be seriously lost without it.

The second problem is that Exchange still has to do a lot of extra work when using stub archives.  It still has to index and store the data and the Information Store will become extremely busy.  No matter how good the third party application is, Exchange still does the bulk of the work.

Don't get me wrong, stubbing is a legitimate option in some situations.  What it isn't is a fix-all for everybody.  Larger organizations that process huge amounts of mail are not going to benefit from this solution.  A smaller operation with fewer users who are just on the brink of their storage capacity may find value in using this solution.