A severe Gmail service disruption on Tuesday affected up to 10 percent of users, according to Google.
The outage, which saw up to 35 million users unable to access accounts, lasted just over an hour. The disruption began at 5.42pm BST on Tuesday, Google said on its apps status dashboard.
"We've determined that this issue affected less than 10 percent of the Google Mail users who attempted to access their accounts during the affected timeframe," Google said. "While we have resolved this issue with Google Mail, it's possible that some users may experience message delays because affected accounts weren't available to receive messages."
Google does not give official figures for numbers of Gmail users. However, ZDNet UK understands that around 350 million people use the email service.
Some users of the Ars Technica open forum complained that both work and personal email accounts had been affected.