Finally, none of the existing products could give the user what they really wanted: a single universal mailbox and a single universal address book. In this pre-Internet era, savvy users often had mailboxes on their corporate network, online services such as CompuServe or AppleLink, and perhaps also a number of Bulletin board systems (BBSs). Each email system used its own standards for collecting and storing information, forcing users to run multiple clients to access the different services. Although a single-mailbox system could be constructed by administrators with the use of email gateways, these tended to be expensive and technically challenging to maintain.