Patch Tuesday (maybe) breaks Outlook worldwide

As I am writing this, I hope that all you Outlook users and sending and receiving email without incident?

However, that certainly wasn’t the case on Tuesday of this week, when it was originally thought that a ‘Patch Tuesday’ update included a bug in the ‘Click-to-Run’ component that caused an 0xc0000005 error when starting Outlook. It affected those using an on-premise Exchange server or the Office 365 cloud, and significant number of users worldwide experienced the problem.

It took Microsoft just 9 hours to identify and resolve the issue with an emergency, and they said that in fact it wasn’t caused by the July Windows update batch, although they have not yet said what did cause it.

During the downtime, web and mobile Outlook clients were unaffected. If you use Outlook, perhaps your business continuity plans should include switching to web or mobile as a backup; if your business continuity plans need reviewing (or creating!), do get in touch with me.