Certification Guarantees the Interoperability of Email products that Encrypt Email at the Network Boundary

Redwood City, CA – August 23, 2004 – Tumbleweed® Communications Corp. (NASDAQ:TMWD) today announced that Tumbleweed's Email Firewall 6.0 has received S/MIME Certification from the Open Group, a technology neutral consortium committed to business efficiency and interoperability. Tumbleweed is one of the first two vendors to have an email encryption gateway certified for interoperability under the program, which is designed to reduce the risk of deploying gateway to gateway S/MIME authentication and encryption by ensuring that certified products from a variety of vendors will work together. Secure/Multipurpose Internet Mail Extensions, or S/MIME, was developed in the mid 1990's to prevent the interception and forgery of email through strong authentication and encryption.

The Open Group S/MIME Gateway specification establishes an interoperable profile of the S/MIME v.3.1 specifications from the IETF, adding a lightweight protocol for the exchange and installation of public encryption keys between business partners. Certificates are awarded to vendors for products which are guaranteed to conform to the S/MIMEGateway specification and which have been tested against other certified products. The S/MIME Gateway Certification program was developed by The Open Group in response to a requirement from Massachusetts Health Data Consortium, who's members need to ensure the private of Private Health Information (PHI) to conform to the provisions of the HIPAA regulations.

"Secure messaging is an enterprise imperative for 21st century businesses," said Matt Cain, Senior Vice President of analyst firm META Group. "S/MIME gateway interoperability certification is a large step forward in delivering an industry standard for end-to-end email encryption and authentication. Secure messaging must be part of every organization's email hygiene strategy."

"In addition to providing assurance that encrypted email will work from one Internet domain to another, the S/MIME Gateway specification provides a foundation for strong email authentication,” said Ken Beer, Director of Product Management at Tumbleweed Communications. "Authentication of email senders has emerged as an important cornerstone for many different aspects of email security, including anti-spam, anti-virus, and anti-phishing. Most email threats are reliant on sender address spoofing, so the adoption of authentication technologies, including the S/MIME Gateway profile, can go along way toward cleaning up Internet email for everyone.”

"Tumbleweed's Email Firewall was our choice for email security 3 years ago," said Peg Dreske, Manager Notes/Domino Infrastructure at Tufts Health Plan. "Now that there is proven interoperability with other vendors, we'll be among the first to email securely and easily with other MHDC members at the gateway level. Tumbleweed's interoperability certification reduces the risk for those organizations who have not yet invested in a secure email solution, and proves to those of us who have that we made the right choice."

About Tumbleweed's Email Firewall
Tumbleweed Email Firewall has been recognized as the #1 enterprise software solution for fighting spam according to Network World (http://www.nwfusion.com/reviews/2003/0915spam.html), and the #1 email firewall software for large enterprises by Information Security Magazine. Tumbleweed Email Firewall protects, filters and secures email traffic at the Internet gateway with an integrated set of anti-spam, anti-virus, anti-hacker, content filtering, email relay, and encrypted messaging capabilities -- minimizing email communications risks and reducing email management costs. Tumbleweed Email Firewall is used by over 400 of the largest, most demanding messaging infrastructures in the world, and is available in both appliance and software editions.

About Tumbleweed Communications Corp.
Tumbleweed is a leading provider of secure Internet messaging software products for enterprises. By making Internet communications secure, reliable and automated, Tumbleweed's anti-spam, email firewall, secure file transfer, secure email, and identity validation solutions help customers significantly reduce the cost of doing business. Tumbleweed products are used by millions of end-users and tens of thousands of corporations. Tumbleweed customers include ABN Amro, Bank of America Securities, Catholic Healthcare West, JP Morgan Chase & Co., The Regence Group (Blue Cross/Blue Shield), St. Luke's Episcopal Healthcare System, the US Food and Drug Administration, and the US Navy and Marine Corps. Tumbleweed Communications was founded in 1993 and is headquartered in Redwood City, Calif. For additional information about Tumbleweed go to www.tumbleweed.com or call 650-216-2000.

SAFE HARBOR STATEMENT
Tumbleweed cautions that forward-looking statements contained in this press release are based on current plans and expectations, and that a number of factors could cause the actual results to differ materially from the guidance given at this time. These factors are described in the Safe Harbor statement below.

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 timing of Tumbleweed’s adoption of the Sender ID framework and effectiveness of Tumbleweed products that use the Sender ID framework. 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 15, 2004 and Form 10-Q filed May 10, 2004.

Tumbleweed assumes no obligation to update information contained in this press release, including for example its guidance regarding its future performance, which represents the Company's expectations only as of the date of this release and should not be viewed as a statement about the Company's expectations after such date. Although this release may remain available on the Company's website or elsewhere, its continued availability does not indicate that the Company is reaffirming or confirming any of the information contained herein.

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