Outlook for Mac crashing on startup

Microsoft should certainly be able to walk you through this. But to start, here's a link to the page Barney-15E mentioned in the first response to your topic:

Otherwise, you could try the easiest thing first. That is, if it's just a corrupt preference file that's causing Outlook to crash, you may be able to solve this very quickly.

Close Outlook.

Click anywhere on the desktop so it says Finder as the foreground app next to the Apple logo at the top left of the screen. Next, hold down the Option key and choose Go > Library from the menu bar. Press Command+2 to put that Library folder into list mode. It's just much easier to find things alphabetically.

Open the Group Containers folder. Open the UBF8T346G9.Office folder. You should, at minimum, see these items:

The folder Outlook is where all of your data is. Contacts, accounts, emails, etc. As a safety step, you should first backup this folder to another drive. Then it will be nearly impossible to lose anything important.

From within the UBF8T346G9.Office folder, continue through subfolders Library > Preferences. Delete the file:

UBF8T346G9.Office.plist

Launch Outlook again and see how it behaves.

What you would need to back up first so they can be restored after deleting the container folder items are your contacts, emails you've saved and stored on the local drive (IMAP account), or all emails (POP account).

That, and screen shots of your email account details so you can set them up again. Gmail is done automatically by simply entering your gmail.com account address.

There are many files in the containers folder. My question is the following, which files get deleted?

If Outlook stores your data in the container as Kurt Lang noted, you will need to back that up or not delete it.

The Office Uninstall instructions on Microsoft’s website has a list of all the containers.

Yes, you can contact both Apple Support and Microsoft Support for further assistance with this.

For Apple, just select the "Support" link on the lower left-hand side of this forum's web page.

There are many files in the containers folder. My question is the following, which files get deleted?

You delete the entire container. The app will rebuild it.