The Gmail service there is now known as Google Mail.
A Google representative said that the search giant decided to change the suffix after protracted wranglings with research firm Independent International Investment Research (IIIR), which uses the name G-mail to refer to a part of its financial analytics software.
"We are still working with the courts and trademark office to ensure our ability to use the Gmail name, but this could take years to resolve," the representative said. "And in the meantime, we want our users to have an e-mail address and experience they can rely on. We also want to relieve both Google and our users of the distraction of the dispute."
While all previous Gmail accounts will remain valid, new U.K. users signing up for Google's e-mail service will be given accounts ending in @googlemail.com, rather than @gmail.com.
The search giant, which launched Gmail in April 2004, voluntarily ceded the trademark to London-based IIIR.
IIIR registered the trademark Gmail in the time between Google's Web-based e-mail launch and attempt to trademark the Gmail name.
Google said IIIR "contacted us in June 2004 and claimed rights to 'Gmail' and sought a 'business solution;' in other words, they wanted money." Although no official figure has been put on IIIR's request, Google's representative described the sum as "exorbitant."
In a recent report from IIIR on the name dispute, however, the company said it "considers the proposals it made to Google for settlement of this matter to be fair and reasonable to both parties." In a valuation of the Gmail trademark conducted in a draft discussion document in December 2004, IIIR set the brand's worth at between $44 million and $60 million (25 million pounds and 34 million pounds) although the company later said it would settle for a considerably lower sum.
Google and IIIR entered into negotiations, which soured after IIIR CEO Shane Smith broke the pair's agreement to keep discussions confidential. Google then started its own talks with the press, prompting Smith to provide more details about the ongoing negotiations.
Google, which faces competition for a U.S. patent for Gmail as well, maintains that IIIR's claim is tenuous at best.