Email Issues Effecting Some Users

Office Admin center – Service health

Email access issue in O365 effecting some users
User Impact:
Users may be unable to connect to the Exchange Online service. Current status: We’ve determined that timeouts within the Exchange database infrastructure are causing service availability issues. We’re continuing to investigate the underlying cause and to mitigate impact. 
Wednesday – 29/3/2017
Microsoft have removed this advisory, confirming that the issue is now resolved.