Leading ASP USi Delivers Managed Exchange 2000 Services; Capacities Include Durable-Directory Hosting Service.

Business/Technology Editors

ANNAPOLIS, Md.--(BUSINESS WIRE)--Oct. 10, 2000

USinternetworking, Inc. (USi, Nasdaq:USIX), the leading Application Service Provider (ASP), today announced its E2K Durable-Directory hosting service and confirmed its commitment to delivering the world's premier messaging and collaboration service powered by the Microsoft Exchange 2000 server platform.

USi's E2K Durable-Directory service leverages the Active Directory technology within Microsoft's Windows 2000 operating system and serves as a logical extension to USi's existing messaging and collaboration service built on Microsoft's Exchange 5.5 technology. The E2K Durable-Directory service will enable USi to support enterprise customers by hosting all, or part, of the Active Directory.

"The USi E2K Durable Directory results from significant investment of USi technical know-how aimed at developing the world's leading ASP service offering for Exchange 2000," said Spyros Sakellariadis, Vice President and Chief Technology Officer for USi's Enterprise Applications Business Unit. "USi's E2K Durable Directory is based on hands-on experience and proven methodologies for integrating hosted Exchange 2000 servers with the Windows 2000 Active Directory."

"At ePresence, we have been working very closely with USi to implement a hosted Exchange 2000 solution in support of our international Outlook users - one that will integrate well with our Windows 2000 Active Directory structure," said Scott Kitlinski, Chief Information Officer at ePresence. "We were the world's first company to deploy Windows 2000 globally and we are a market leader in delivering Internet services that personalize e-business - we understand very well the importance of generating internal IT efficiencies using the Windows 2000 platform. That's why we selected USi to implement Exchange 2000 services in support of international remote Outlook users."

"The Durable-Directory is a clear example of USi's leadership position in the ASP market and their deep understanding of the Microsoft Exchange 2000 platform," said Stan Sorensen, group product manager, Server Applications at Microsoft. "USi's expertise as an application service provider combined with Exchange 2000 will provide enterprise customers with a reliable, scalable hosted messaging and collaboration infrastructure."

Pricing for Exchange 2000 services is now available.

About USinternetworking, Inc.

USinternetworking Inc. (Nasdaq: USIX) is a leading Application Service Provider delivering e-commerce and enterprise software as a service. The Company's iMAP portfolio of service offerings delivers the rich functionality of leading software from Ariba, BroadVision, Lawson, Microsoft, Oracle, PeopleSoft, and Siebel as a continuously supported, flat rate monthly service via an advanced, secure global data center network. USi's AppHost service enables Independent Software Vendors to effectively provide their customers with software products as Internet-based services.

Internet Managed Application Provider, iMAP, AppHost, PriorityPeering, USiGSP, USiSAN USiAccelerate, and Making Software Simple are service marks of USinternetworking, Inc. All other trademarks are the property of their respective owners. USi strategic partners and providers are publicly traded on Nasdaq under the symbols: ARBA, BVSN, CSCO, MSFT,ORCL, PSFT and SEBL.

Information in this release may involve expectations, beliefs, plans, intentions or strategies regarding the future. These forward-looking statements involve risks and uncertainties. All forward-looking statements included in this release are based upon information available to USinternetworking Inc. as of the date of the release, and we assume no obligation to update any such forward-looking statement. The statements in this release are not guarantees of future performance and actual results could differ materially from our current expectations. Numerous factors could cause or contribute to such differences. Some of the factors and risks associated with our business are discussed in the Company's registration statement on Form S-3 declared effective by the Securities and Exchange Commission ("SEC") on June 13, 1999, the Company's Form 10-Q filed with the SEC on August 15, 2000, and in our other reports filed from time to time with the SEC.