Messages from Gmail sent Monday indicated that they were encoded with, as evidenced by logs in the message headers. When an e-mail header from a Gmail message was opened, a code reading "DomainKey-Signature" appeared.
DomainKeys is a technology backed by Yahoo that tries to cross-check e-mail messages to verify their origination. The idea is to thwart e-mail "spoofers," which are spam messages that pretend to be from legitimate Internet addresses. These spoofed e-mails often pass through spam filters and fool recipients into opening the messages.
"We are encouraged by the adoption of DomainKeys and believe it is a key step in furthering the industry's fight against spam and e-mail forgery," Yahoo spokeswoman Mary Osako said. "Spam is an industry issue, and we believe collaboration with the Internet community is vital in solving the authentication issue."
A representative from Google was not immediately available for comment.
DomainKeys is a proposed system that attaches encrypted digital tags to each e-mail, then compares them to a public database of legitimate Internet addresses. Once the message arrives, the database and message keys need to match in order to pass into an e-mail in-box.
Yahoo is not the only Web giant to propose an antispam system. Microsoft has been pushing, which verifies the authenticity of the sender's "@" address by checking the message's numeric Web address. Sender ID blends Microsoft's proprietary " " with another technology, called Sender Policy Framework, or SPF.
America Online has put its weight behind SPF and has begun installing the system into its e-mail servers. The online giant recentlyafter standards bodies and the open-source community pulled their support and criticized Microsoft for keeping the technology under a shroud of secrecy. AOL is still testing DomainKeys, which works in concert with SPF or SenderID.
All three companies are standing behind separate technologies and have each filed proposals to the Internet Engineering Task Force for standardization.
For Google, the addition of antispam technology is the latest step by the search giant to beef up its e-mail service. The company in April beganand launched it with 1GB of mail storage, sending shock waves across the industry. Soon after, and .
Gmail's adoption of DomainKeys also could add legitimacy for Yahoo's pursuit of standardization.
CNET News.com's Stefanie Olsen contributed to this report.