Cannot start Microsoft Outlook, the command line argument

Some possible solutions to the “Cannot start Microsoft Outlook, the command line argument is not valid, Verify the switch you are using” error message in Microsoft Outlook on a Windows PC are: -Check the command line argument you are using to see if it is valid.

Cannot start Microsoft Outlook, the command line argument is not valid

Outlook’s Safe Mode can help diagnose problems with your Microsoft Outlook by starting up with only essential features and components. This can be helpful when you’re experiencing an issue due to a corrupted add-in. To start Microsoft Outlook in Safe Mode, press Win+R to open the Run prompt and run this command:

Outlook /safe

It will prompt you to choose a profile to use. Select a profile from the drop-down menu and click the OK button.

Open Microsoft Outlook in Safe mode to start with add-ins disabled. This means that some add-in is creating the problem. You will have to identify the bad add-in and disable or remove it.

Select COM Add-ins from the bottom drop-down menu, and click the Go button. You will be able to enable, disable, or remove COM Add-ins from here: File > Options > Add-ins.

Once you have done the needful, close the Outlook window and try to open it normally.

Use Microsoft Outlook Inbox Repair Tool

The Outlook Inbox Repair Tool can repair corrupt PST files so that you can open Outlook without getting any errors. To use this tool, navigate to this path:

C:\Program Files\Microsoft Office\root\Office16

Or,

C:\Program Files (x86) \Microsoft Office\root\Office16

To repair a corrupted PST file, you can use the SCANPST.EXE program. To open the program, double-click on the SCANPST.EXE file.

Now, click the Browse button and select the backup file. Click the Start button to start repairing.

Reinstall Outlook

Last option: repair or reinstall Microsoft Outlook If none of the solutions worked for you, the last option is to repair or reinstall Microsoft Outlook. To repair Office programs, open Control Panel > Uninstall a program.

Right-click on Office > Change. Choose your options to repair Office programs.