The Web portal and ZixIt, an encryption company based in Dallas, confirmed that they have inked an agreement to provide encryption to Yahoo Mail users but declined to comment further.
The companies did not disclose a start date for the service. Yahoo Mail began carrying a link to ZixIt's ZixMail page this week but said that link was part of its regular advertising.
When the system launches, it will let Yahoo Mail account holders send messages through ZixIt's SecureDelivery.com site, scrambling messages so only sender and recipient can read them, even if the message is intercepted en route.
ZixIt's SecureDelivery site this quarter will launch software add-ons for use with Lotus Notes and Microsoft's Outlook email application.
The deal will make Yahoo the first major portal to offer encrypted email. So far, data scrambling has been the province of tech-savvy computer users willing to use products that require a software download, such as Network Associates' Pretty Good Privacy.
ZipLip, which offers a variety of secure messaging products in addition to its free mail site, said Yahoo's move shows that mainstream encryption's time is coming.
"Yahoo has gotten an understanding that consumers do need more privacy," said ZipLip chief executive Kon Leong. "They are addressing the consumer market, so the timing is right."