Exchange's uneasy dominance "On the customer side of the equation, Microsoft is painfully aware that no more than one-quarter of its Exchange 5.5 installed base has upgraded to Exchange 2000, in spite of that latter version's having been on the market for more than two years. Users' beefs with Exchange 5.5 and Outlook include the products' premium pricing, performance and scalability problems; substandard offline access functionality; inflexible public folders; and vulnerability to viruses and spam."