If the Outlook client starts to work strange, one of the first things to see is whether add-ons cause the problem. To disable them, let them know if they are the problem.
What is add-on?
Add-ons are extra bits of functionality that software vendors create to plug their applications into Outlook. You can install extensions yourself by opening Outlook and clicking Home> Get Extensions, which shows some of the add-ons available to you.
But most add-ins are automatically installed when you install a software on your computer. You should never use the add-on, or even be aware that they are there, but they are not (usually) malicious code or something nasty. They are intended to make it easier for you to use a product. For example, when you install Adobe Acrobat PDF reader, it installs an Outlook add-in that allows you to make PDFs based on email.
There is usually no need to remove extensions, but if Outlook starts to work strange, especially if it freezes, crashes or refuses to open. Then the add-on will be disabled to tell if they are the problem.
How to disable all extensions
Troubleshooting is about finding the cause of a problem. The best way to do this is to gradually limit the possible problems until you are left with just the cause of the problem. In the case of Outlook problems, disabling all add-ons means that if the problem is resolved, enable the add-on one by one to identify which causes the problem. This is especially true if Outlook encounters problems at startup.
The easiest way to disable all extensions at once is to open Outlook in Safe Mode. This disables all extensions but does not change anything else, so if one (or more) add-ons causes the problem, everything works as expected in Safe Mode. There are several ways to open Outlook in Safe Mode, depending on which version of Outlook and which version of Windows you use. There are a few methods that should generally work over all combinations of supported versions of Outlook and Windows, but if they do not work, you can search online for your specific combination.
Method one: Hold the Ctrl key while starting Outlook
This works if you click an icon on the taskbar, desktop, or Windows menu. Hold down the CTRL key on the keyboard while clicking the Outlook icon (or double-clicking the icon on the desktop). A confirmation message is displayed.
Click "Yes" to open Outlook in Safe Mode.
Method two: Use the Run dialog box or Windows 10
In Windows 10, press the Windows key or in Windows 7 or 8, press the Windows key + R. In Windows 10, it will download the Windows menu where you can write commands directly and in Windows 7 or 8, it will bring up the Run dialog, where you can also write driving commands. Anyway, type "outlook.exe / safe" (without quotes) and then press Enter.
Select the profile you want to open (for most people there will only be one "Outlook" profile to choose) and then click "OK". This opens Outlook in Safe Mode.
Whatever method you choose, Outlook will be open in Safe Mode. The program name in the main field changes from "Microsoft Outlook" to "Microsoft Outlook (Safe Mode)."
All of the add-on will be disabled, except for some common Microsoft Office extensions. This is very unlikely to be the cause of an Outlook issue, but you can manually disable them when Outlook is open. The next time you open Outlook as usual (ie not in Safe mode), the extension will be re-enabled if you have not manually disabled them.
How to disable individual extensions
Starting in Safe Mode will tell you if one of your add-ons is the problem, but if you want to disable a single add-on, such as one that has just been installed or a kernel Microsoft add-on that doesn't is disabled in Safe Mode – you can also do so. Click File> Options and then click on the "Add-ons" category to the left.
This opens the additional section. To enable or disable extensions, make sure that "COM Add-ons" is selected in the drop-down menu (it is default so you don't need to change it) and then click "Go."
This opens the COM Extensions dialog, where you can enable or disable add-ons.
Activating and deactivating is an exercise-a check box which means that the extension is enabled; no cross means that the extension is disabled. To disable an extension, deselect it and then click "OK".
] Important: Make sure you do not click "Delete". This will uninstall the selected extension, not disable it!
When you return to File> Options> Add-ons, Disabled, you will be visible in the Disabled Add-On section.
The extension will remain disabled until you enable it again. Test to see if your problem occurs when the add-on is disabled. If it does, continue disabling your add-ons one by one until you find the culprit.
How to Enable Individual Extensions
Once you have elaborated which add-on causes the problem (if any), you can enable any other add-ons that you disabled. Enabling individual extensions is so easy to disable them: click File> Options> Add-ons, make sure "COM Extensions" is selected in the drop-down menu, and then click "Go" to open the COM add-in dialog.
Select the extensions you want to enable and then click "OK". You may have to restart Outlook for the extension to load, and it is generally a good idea to do so anyway to make sure everything is working properly.
You can disable and enable extensions when troubleshooting an Outlook problem. They are not always the cause, but if Outlook has worked well and then a problem arises after a new extension has been installed, it is a good place to start looking.