Google's popular email service - Gmail went down worldwide, affecting 350 million users.
Many Gmail users received error messages on their accounts, meaning they could not send or receive email or access their inboxes on Tuesday.
Google acknowledged the problem and tweeted that they had received several reports of errors, The Telegraph reports.
The firm said it was 'investigating reports of an issue' with Gmail, and issued a statement as the service was being restored.
"We're aware that some users are experiencing an error when accessing their Gmail. We are working on a resolution and apologize for the inconvenience. Thanks for your patience," Google said.
Gmail, which claims to have over 350 million active accounts, said overall fewer than two percent of its users were affected worldwide.