Google is gaining ground with enterprises that have 5,000 or more seats, Gartner said, naming several public- and private-sector users with more than 10,000 Gmail seats.
Big organizations that use Gmail include Motorola Mobility, with 22,000 users; the U.S. General Services Administration, with 17,000; the , with 17,000; automaker Jaguar Land Rover, with 15,000; the InterContinental hotel chain, with 25,000; and , with 10,000.
"We are at the start of a in the war of the email clouds," wrote Gartner analyst Matthew Cain, in a report on Google's enterprise progress that was released Friday.
-based email systems account for about 4% of the overall enterprise email market, according to the research firm.
Microsoft released a cloud-based Exchange service in 2010, and a more expansive cloud offering, Office 365, this year.