A major Microsoft Office 365 outage in the Houses of Parliament that left up to 3,000 users without email was due to Microsoft failing to inform itself about a technical change, The Register can reveal.
The outage occurred on 23 June and resulted in a total of 13 hours of downtime, the Parliamentary Digital Service said in response to a Freedom of Information request.
The blunder led to a number of emails vanishing and reportedly took several days to fix.
The PDS estimated that the outage in June affected 30-50 per cent of its 6,000 users trying to access email.
"The issue in June was caused by a technical change made by Microsoft to part of Microsoft's Office 365 Exchange environment," said the PDS in its FoI reply. "The change introduced an issue which prevented some users connecting to the Office365 service through Outlook and/or ActiveSync."
"Microsoft's UK Premier support team had not known about the change, the issue, nor the resolution at the time, and only discovered the root cause retrospectively," it added.
"The team that had made the change reversed it, once they had realised it wasn't working quite correctly, but did not advise the Premier support team of their actions. Microsoft have been transparent with us in their admission of fault over this issue."
Parliament made the move to Microsoft Office 365's cloud-based email service in May this year. The Register understands the transition slashed costs by hundreds of thousands of pounds, halving monthly user fees from roughly £25 per month to £12 per month.
The British legislative house also recently dished out 600 iPads to MPs and peers as part of its digitisation plans.
Parliament's previous email system was no stranger to outages, with a botched upgrade last year causing a number of web outages. ®