iBasis Delivers Messaging Solutions to Major Wireless and Wireline Carriers

Openwave Transitions Unified Messaging Service Infrastructure and ASP Customers, Including More Than One Million Users, to iBasis

BURLINGTON, MA - May 29, 2001 - iBasis, Inc., (Nasdaq: IBAS), the leader in advanced Internet-based voice communications, today announced that it is providing messaging services to several major wireless and wireline carriers. These carriers bring more than one million messaging subscribers and immediate service revenue to iBasis.

iBasis has integrated OpenwaveTM Unified Messaging into its VoCore^SM hosted messaging solution for wireless and wireline carriers. VoCore is a comprehensive portfolio of hosted, high-margin communications services, including phone-based access to email, voicemail, and faxmail, PIM (integrated personal scheduling and contact management), and personalized communications portal services, based on the OpenwaveTM Unified Messaging solution. VoCore is a flexible solution that allows service providers to select the features best suited to their customers' messaging needs. iBasis will offer its VoCore solution to its more than 110 carrier customers worldwide, and with Openwave, will jointly market VoCore to Openwave's carrier customers as an outsourced enhanced communications solution.

As a global ASP partner for Openwave, the worldwide leader of open IP-based communications infrastructure software and applications for carriers, iBasis has assumed ownership and management of the Openwave ASP infrastructure that enables immediate messaging service delivery. This service infrastructure includes an Openwave data center in Santa Clara, California and 19 remote service facilities in the U.S. and Canada.

"As a global ASP messaging provider for Openwave, delivering service to some of Openwave's largest carrier customers, iBasis is establishing a leadership position in outsourced enhanced communications services," said Ofer Gneezy, president and CEO of iBasis. "Our VoCore solution is now the power behind the enhanced services of some of the world's best-known carriers. Our success with VoCore will complement our strength in international voice and speech services. As the provider of choice for many of the world's largest carriers and enterprises, we offer our customers a reliable `one stop shop' for high quality, global voice services."

"Openwave is pleased to work with iBasis, an innovator and leader in Voice-over-IP services, to deliver a hosted solution for Unified Messaging," said Don Listwin, president and CEO, Openwave Systems. "This ASP solution, which incorporates technology from Openwave, Cisco, and iBasis, enables carriers to quickly integrate messaging services while providing an expansion path to a new generation of voice services built upon VoiceXML in the near future."

"As customer churn increases and service margins for traditional and wireless carriers erode, the demand from carriers for higher margin, enhanced voice services will continue to grow," said Megan Gurley, senior telecommunications analyst at The Yankee Group, a leading industry analyst firm. "Hosted solutions such as iBasis VoCore can help carriers reap the benefits of value-added services, providing greater feature/function flexibility and reduced time-to-market, while avoiding the costs and complexities associated with the engineering, provisioning, service management and billing requirements of these enhanced services."

Guidance
The following statements are forward-looking and actual results may differ materially due to factors noted below, among others. The information provided in this financial outlook is as of May 29, 2001, and it is currently expected that this financial outlook will not be updated until the release of iBasis' next quarterly earnings announcement. iBasis undertakes no obligation to update this information. iBasis reserves the right to update this financial outlook at any time for any reason.

The company reiterates its most recent guidance for 2001. iBasis anticipates total 2001 revenue in the range of $150-160 million, inclusive of enhanced services, and believes that it will achieve positive EBITDA in the fourth quarter of 2001. iBasis believes that it continues to be fully funded for growth through profitability, with positive net income targeted for the first quarter of 2002. The company believes enhanced services will comprise roughly 20% of total quarterly revenue each quarter for the remainder of 2001. The company's overall steady-state gross margin target is 25%-35%. iBasis expects steady-state gross margin target in the core VoIP business to be 20-25%.

The company anticipates that in the second quarter it will take an aggregate charge of approximately $35 million. This charge includes the write-off of fixed assets and associated contractual obligations relating to certain non-revenue generating ICOs and data centers, as well as severance expense in connection with a reduction in force.

The iBasis Network: A Carrier-Class Global Infrastructure For Enhanced Services
The iBasis NetworkTM is a robust, global platform for the delivery of IP-based communications services, including wholesale, phone-to-phone VoIP and enhanced services, such as messaging and speech-enabled business solutions. With a carrier-class infrastructure in 65 countries and through its relationships with other communications providers, iBasis can provide voice services virtually anywhere in the world.

About iBasis
Founded in 1996, iBasis (Nasdaq: IBAS) is the leader in advanced Internet-based voice communications. iBasis delivers toll quality international voice services and provides the infrastructure for hosted communications solutions, including messaging and speech-enabled content, e-commerce and customer service applications. The company's customers include many of the largest enterprises and carriers in the world, including AT&T, Cable & Wireless, China Mobile, China Unicom, Concert, ExxonMobil, Gannett, H&R Block, Home Shopping Network, Morgan Stanley, NTT, Telstra, Sabre Group, Sprint, Western Union, WorldCom, and Verizon. iBasis' hosted, enhanced service solutions include SpeechPortTM, a scalable, customizable ASP environment for speech-enabled business solutions, VoCoreSM messaging and the IP CallCardTM pre- and post-paid calling card platform. The iBasis Network is the world's largest international Cisco Powered Network for Internet Telephony and the first to receive the Unified Communications-Cisco Powered Network (UC-CPN) designation. iBasis is listed in both the Russell 2000® and Russell 3000® Indexes. The company can be reached at its worldwide headquarters in Burlington, Mass., USA at 781-505-7500 or on the Internet at http://www.ibasis.com .

About Openwave
Openwave Systems Inc. (Nasdaq: OPWV) is the worldwide leader of open IP-based communication infrastructure software and applications. Openwave is a global company headquartered in Redwood City, California. For more information, please visit http://www.openwave.com/ .

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Assured Quality Routing and iBasis are registered marks, VoCore is a service mark, The iBasis Network, Internet Central Office, Internet Branch Office, IP CallCard, SpeechPort, IPort, and PriceInteractive are trademarks of iBasis, Inc. or its subsidiaries. Cisco and Cisco Powered Network are registered trademarks of Cisco Systems, Inc. All other trademarks are the property of their respective owners.

Except for historical information, all of the expectations, projections and assumptions contained in the foregoing press release, including those relating to the company's current expectations regarding revenue growth, sources of revenue, margin improvement and future capital expenditures constitute forward-looking statements under the Private Securities Litigation Reform Act of 1995 and involve risks and uncertainties. Important factors that could cause actual results to differ materially from such forward-looking statements include, but are not limited to, (i) the extent of adoption of the company's new voice-based Internet services and the timing and amount of revenue generated by these services; (ii) fluctuations in the market for and pricing of VoIP services; and (iii) the other considerations described as "Risk Factors" in iBasis' Annual Report on Form 10-K for its fiscal year ended December 31, 2000, and the company's other SEC filings.