Diamond Computer Service Adopts Tumbleweed's Integrated Messaging Exchange for Payment Slip Distribution

REDWOOD CITY, CA - April 5, 2001 - Tumbleweed Communications K.K., a provider of Internet messaging solutions for secure online business transactions, and Diamond Computer Service Co., Ltd. (DCS), one of Japan's largest systems integrators, announced today that DCS has adopted Tumbleweed's Integrated Messaging Exchange (IME™) 4.06J platform for its new SecureMail Service. DCS, affiliated with the Tokyo Mitsubishi Bank Group, will introduce SecureMail, an Internet-based payment slip distribution outsourcing service, in April 2001.

Tumbleweed IME is a platform and set of applications for creating secure email channels between an enterprise and its customers, partners and suppliers. IME 4.06J is the localized Japanese version of IME. The new service being offered by DCS is designed to move paper-based processes online securely.

DCS will provide secure universal delivery, tracking and auditing capabilities for high-volume delivery of financial statements enabled by IME. IME differs from other secured email software in that there is no need for both parties to an email exchange to have the same security software installed in their systems. This allows recipients to use their normal emailer and browser to view correspondence.

DCS provides an extensive outsourcing service primarily focusing on financial institutions and credit card companies, and also provides outsourcing payroll calculation service. "Our requirements for starting a new service that delivers payment statements and other forms via the Internet were a high level of security and delivery confirmation functions," explains Diamond Computer Service Managing Director, Satoshi Ohta. "We selected Tumbleweed's IME, because it is a product that fulfills all of our requirements. We plan to link IME with our existing Internet-based e-commerce and other systems to offer clients effective distribution solutions."

"Extremely high security and delivery confirmation are essential to the delivery of financial information on the Internet. Tumbleweed IME with its clear security and trackability, is quickly becoming the de facto standard for secure Internet delivery in Japan," said Jeffrey C. Smith, CEO, Tumbleweed Communications Corp. "We are pleased that DCS has chosen Tumbleweed IME for the safe and efficient delivery of its clients' documentation."

About Tumbleweed
Tumbleweed Communications (NASDAQ: TMWD) is a leading provider of mission critical messaging solutions that create and manage secure two-way communications channels. Tumbleweed's customers use the company's solutions to define secure communication networks, to centrally control and monitor the corporate communications stream and to create a foundation for automated preparation and secure Internet delivery of sensitive business information. Companies that rely on Tumbleweed Communications solutions include American Express, Chase Manhattan Bank, Chevron, Datek Online, the European Union's Joint Research Council, FDA, John Deere, Merrill Lynch, Nike, Northern Trust, NTT, Salomon Smith Barney, Travelers, United Parcel Service, and seven of the world's largest postal services. Tumbleweed Communications was founded in 1993 and is headquartered in Redwood City, CA.

Diamond Computer Service Co., Ltd
Diamond Computer Service (DCS) separated from Mitsubishi Bank (now the Bank of Tokyo- Mitsubishi) in 1970. The company listed its stock on the Second Section of the Tokyo Stock Exchange in 1993, and celebrated its 30th anniversary in July 2000. For over 30 years DCS has provided high quality, reliable, and effective services in system integration (from planning and development of computer systems to implementation and maintenance) and outsourcing.

Except for the historical information contained herein, the matters discussed in this press release may constitute forward-looking statements that involve risks and uncertainties that could cause actual results to differ materially from those projected, particularly with respect to the security features of Tumbleweed's products and the activities of any third party. In some cases, forward-looking statements can be identified by terminology such as "may," "will," "should," "potential," "continue," "expects," "anticipates," "intends," "plans," "believes," "estimates," and similar expressions. For further cautions about the risks of investing in Tumbleweed, we refer you to the documents Tumbleweed files from time to time with the Securities and Exchange Commission, particularly Tumbleweed's Form 10-K filed March 30, 2001 and Form 10-Q filed November 13, 2001. Tumbleweed assumes no obligation to update information contained in this press release.