When launching Outlook you may receive the following error.
This error could occur from a number of different reasons.
Disable the Add-ins
One possibility–and always the first thing to check–is that an Outlook add-in could be causing the error. To determine if this is the root cause open outlook in Safe Mode.
To do this, hold the CTRL key on your keyboard while clicking the Outlook icon. You will receive a prompt asking whether you want to open Outlook in safe mode. Click Yes.
Outlook will then launch with all add-ins disabled. Furthermore, the reading pane and any toolbar customization will be disabled. You can then navigate to File >> Options.
Once in options select Add-Ins. From here you can see all add-ins that load when Outlook is opened in normal mode. To disable an add-in click the Go… button.
From the Add-Ins dialog, you can deselect an add-in to disable it. Click Ok then restart Outlook. You can repeat this process until you find the add-in preventing Outlook from starting
Corrupt OST file
This error can also occur if you are using cached mode in Outlook and your OST file has become corrupt. The OST file is an offline cache of your Exchange mailbox. It works similarly to how the cache works in your web browser. Rather than fetching a new copy of a web page every time you visit a website your browser caches a copy of that web page instead. Outlook caching works roughly the same way. A copy of all your emails is cached in a local file on your computer. The difference with Outlook is that the cache is just one giant file versus the tens of thousands of tiny files your browser cache creates. Both technologies use caching to improve the user experience.
So how do we fix a corrupt cache file? The simplest solution? Delete the cache file.
With an Exchange account, all your mail is actually stored on the Exchange server. This means that deleting the OST file has zero implications, except maybe the wait as the cache rebuilds.
For Windows 7, 8 and 10 the OST file is typically located under the following path.
Keep in mind that AppData is a hidden folder. To see this folder you will have to navigate to Folder Options >> View tab >> Show Hidden Files. While in the Folder Options dialog box it is also a good idea to deselect Hide extensions for known file types. That way you can make sure you are deleting the correct file.
Right-click the OST file and select Delete from the context menu.
Open Outlook and give it time to rebuild your Outlook cache. How long this rebuilding process takes depends on your network connection to the Exchange server and the size of your mailbox.
Corrupt PST file
A corrupt PST file can also prevent Outlook from starting. To fix a corrupt PST you launch the SCANPST tool that ships with Outlook. The location of this utility will vary based on the version and edition of Office you are using. Default paths are listed below.
Office 365: C:\Program Files\Microsoft Office\root\Office16\scanpst.exe
64-bit Windows: C:\Program Files\Microsoft Office\Office16\scanpst.exe
32-bit Windows: C:\Program Files (x86)\Microsoft Office\Office16\scanpst.exe
Office 365: C:\Program Files\Microsoft Office\root\office15\scanpst.exe
64-bit Windows: C:\Program Files\Microsoft Office\Office15\scanpst.exe
32-bit Windows: C:\Program Files (x86)\Microsoft Office\Office15\scanpst.exe
64-bit Windows: C:\Program Files\Microsoft Office\Office14\scanpst.exe
32-bit Windows: C:\Program Files (x86)\Microsoft Office\Office14\scanpst.exe
Once you have located SCANPST.EXE double-click to launch the app. This opens a dialog called the Inbox Repair Tool. Click Browse… and locate your PST file. Click Start.
(Your PST is most likely located in C:\Users\<username>\AppData\Local\Microsoft\Outlook\)
The Inbox Repair Tool will then check the PST file for errors. How long this takes will depend upon the size of the PST file.
The Inbox Repair Tool will then report what errors it has found and grant you the option to repair the PST. By default, it will also make a backup of the file before it initiates a repair. You can click Browse… to set the destination for this file. I recommend keeping this option checked. Click Repair. How long this takes will depend upon the size of the PST file and the extent of the corruption.
Once the repair is complete, click Ok. It is recommended to rerun the Inbox Repair Tool a second time to see if any corruption remains. Once all clear you should be able to open Outlook.
Checking Event Viewer
Event Viewer is a great diagnostic tool. To launch Event Viewer click the Start button and type ‘Event’. This should find Event Viewer or View Event Logs. Select either one. On older operating systems navigate to Control Panel >> Administrative Tools >> Event Viewer.
Once open expand Windows Logs and select Application. In the Source column looking for Outlook, Application Error or Windows Error Reporting is a good place to start. In ours, we found all three but one, in particular, gave us an interesting place to start. This error referenced one of our Outlook Add-Ins.
Create a new profile
If others can use Outlook on this PC–and none of the fixes above have helped–then there could be a problem with your Outlook profile. Rather than delete the existing profile, let’s first ascertain whether a new profile fixes the problem.
To create a new mail profile open the Control Panel and double-click Mail. If Control Panel is in category view select User Accounts >> Mail.
Click Show Profiles…
This will list all the profiles configured in Outlook. For my lab I have multiple but most people will only have one profile. Click Add…
Give your profile a name and click Ok.
You will then be presented with the account creation wizard. How you configure your account will vary based on your environment.
Once your account is created you will be back to the Profile screen. Select Prompt for a profile to be used. Click Ok.
At this point launch Outlook and select your new profile. Click Ok.
It will take a few moments to create the new profile and retrieve mail. If this works great. You can now go back into the Control Panel >> Mail >> Show Profiles and remove your old profile. If not, you may need to repair or reinstall Office.
When all else fails–repair Office
If none of the above methods work, or, no one on the computer can use Outlook you most likely need to reinstall Office. You can try a repair of the installation first. But if this doesn’t work a full uninstall and reinstall may be in order.
To repair Office navigate back to the Control Panel. Double-click Program and Features in icon view. Locate Office in your list and click Change.
Using Office 2013 as an example you would select Repair and click Continue. The repair process begins and may take several minutes.
Once complete click Close. You will then be prompted to reboot your PC. Click Yes.
Once rebooted see if the problem persists. If it does, you may have a larger issue at hand such as a corrupt operating system, or, a Windows Update gone amuck. Hardware could also be an issue, or, there may be a problem with your Windows profile.
How about you? What fixes have you found for the error in question? Drop a comment below.