UPDATE: Deferrals from Office365

3:00PM Pacific — Microsoft has traced the problem to an issue within Exchange Online Protection, but has been unable to determine the exact cause of these deferrals.  Microsoft has escalated the issue to their higher level engineers.  It is possible they have also made some configuration changes, as we have noticed a significant reduction in the number of deferrals we’re seeing from Office 365.  We will continue to post updates here as they become available.