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Outlook crashes thanks to Microsoft mistake

Microsoft has made a major blunder with the July patches for Office.  An update can crash Outlook for Windows entirely and the reason for the problem makes the bug especially humiliating for Microsoft.

We’ll explain Microsoft’s blunder, what you can do if affected and how to avoid the buggy patch.

Outlook for Windows tries to start but crashes with an exception code  0xc0000005  .  Retries to start might get a message saying “Outlook couldn’t start last time. Safe mode could help you troubleshoot the problem ..”  Except that Outlook won’t start even in Safe mode.

A buggy patch

Microsoft hasn’t fully explained what happened and what they’ve said doesn’t fit with the publicly known facts.

The problem appears to have started with one of the July updates for Office.  These are pushed out by Microsoft and often installed automatically by people and organizations.

Around the same time as the July updates went out Outlook for Windows started showing errors for customers around the planet. It seems that trying to connect to Exchange Server could make Outlook crash.  Exchange Server means anyone using Office 365 hosted email and possibly / Hotmail etc.

You read that right – using Microsoft Outlook to connect with Microsoft Exchange Server caused the fault.

Microsoft is being vague about who is affected and in what exact circumstances.

At the moment Microsoft is insisting that “This problem is not associated with any of the 7/15/2020 security patches so there is no need to uninstall them if Outlook will not launch.”.  But that doesn’t fit with the timing of the July updates and the Outlook problems.  Many people have restored Outlook by rolling back to a pre-July 2020 update state (see below) which strongly suggests there’s a link with the latest patches.

Unconfirmed reports said that uninstalling the patch for KB4565463 fixed the Outlook problem.

Fix is out now

Microsoft has moved fairly quickly to roll out a fix.

Not fast enough to avoid trouble for people and organizations all over the world.

According to Microsoft:

“A fix has been published but will take time to propagate to worldwide availability.   Outlook will automatically look for the fix on launch …”

You can try to start Outlook, cross your fingers and hope that the fix will be enabled.

If Outlook still doesn’t start correctly, Microsoft suggests waiting a few hours and try again.  In the meantime, Outlook Web Access and mobile email apps will still work to reach a mailbox.

What to do

If Office hasn’t been updated, pause updates right away.  Give Microsoft time to figure the whole problem out and ensure their quick fix doesn’t have unintended consequences.

In any Office program go to  File | Account and choose Disable Updates.

Make a note for a week or 10 days from now to enable updates.  By then Microsoft should have sorted themselves out and fully published any fixes.

It’s tiresome but we’ve long recommended NOT updating Office immediately new patches become available.  See Why updating Office is like the Kobayashi Maru a ‘no win scenario’ and Two ways to stop Office automatic updates


Before Microsoft published their fix or even admitted their error, people around the world found workarounds.  While these might be unnecessary now, they are remedies worth keeping in mind for the next time Microsoft screws up. (there will be a next time …)

Click to Run installs of Office 365 and Office 2019 can be rolled back to a previous version.

Customers affected by the latest Outlook bug got running again like this:

Open a Command Prompt window with Admin access (just in case).

Run these commands:

cd “\Program Files\Common Files\microsoft shared\ClickToRun”

officec2rclient.exe /update user updatetoversion=16.0.12827.20470

or as a single line this does the same thing.

“%Programfiles%\Common Files\microsoft shared\ClickToRun\officec2rclient.exe” /update user updatetoversion=16.0.12827.20470

This will rollback the installed version of all Office apps, not just Outlook.

How did this happen?

How could Microsoft release a patch that’s apparently not properly tested to work with their own services?  Good question and we’ll probably never hear the whole story.

Office updates are tested but there are inevitably mistakes with such complex programs.  But this is such a common, widespread and heavily marketed option that’s it’s hard to understand how it slipped through testing.

Microsoft’s communication and response has been poor.  There’s never been a proper procedure to handle buggy patches so customers are inevitably left floundering and losing money.  Vague messages on Twitter with mentions, but no links, to more information is not proper communication.

We’d call this mistake embarrassing but we know from long experience that Microsoft isn’t capable of corporate embarrassment.  This big boo-boo will be quickly forgotten by all at Redmond.

Why updating Office is like the Kobayashi Maru a ‘no win scenario’

April 2020 updates for Office come with a warning

Two ways to stop Office automatic updates

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April 2020 Office security bug fixes

Office 2016 bug fix pulled because it was buggy!

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