The search giant on Thursday confirmed the outage after some people complained they couldn't access their e-mail accounts. Problems were also reported with Google Desktop.
Nathan Anderson, a user of Gmail (as the service is known outside the U.K., where legal issues), said he was shut out of the mail service for at least three hours.
"I have tried through a number of different ISPs including my BlackBerry and nothing works," he told ZDNet UK.
By midmorning on Thursday users were reporting the service as being back to normal, although many were questioning the root of the problem. A Google representative declined to comment, other than to say Google was "investigating this."
Back in March, several Google Mail users complained that they were struggling to use the free service. Two said their accounts had actually been deleted.
The search giant eventually admitted some accounts had indeed been wiped, but claimed it was not responsible.
David Meyer of ZDNet UK reported from London.