Sometimes there are also problems with Outlook mail; in this case, you can use the safe mode, which can be activated with the “outlook/safe” command. Outlook can be started from the command line [Win+R] as described above.
After startup, you have to select the user profile and press OK to save it. Once you’re done, go to File | Settings | Plugins and deactivate all active plugins – but first, write down on a piece of paper what the ones you “ticked” were.
After switching off the plugins, restart Outlook in normal mode. If the error has been resolved, then switch the plug-ins back on one by one; this will reveal which ones are faulty. If the problem still persists, turn off the macros in the Security Centre and see if Outlook now works without error. If the error persists, the last resort is to reinstall the mail program completely.