Is there any way to FORCE removal of an unwanted shared mailbox from Outlook?

[Jeffl1000]

I very much want to get a no-longer-needed shared mailbox out of everyone’s Outlook 365, and have found it to be impossible using available documentation.  When you try to close it, it tells you to remove it from account settings.  But it’s not there … just the primary account.  I saw in one article that you can remove it by removing the permissions from the mailbox in Exchange, but this didn’t work either.  Is there any registry or powershell script workaround?

[#2]

Is this for Exchange Online or? For the cloud version, you can do it simply via:

Remove-MailboxPermission shared –ClearAutoMapping

If for on-premises, you need to remove all users with Full Access permissions and re-add them with the -AutoMapping flag disabled.

[#3]

I added a user manually (all full access users had been manually removed previously), then successfully executed the two commands at https://www.nucleustechnologies.com/blog/remove-outlook-auto-mapping-for-a-mailbox-in-exchange/#:~:t... It made no difference at all. The problem mailbox remains fixed in exerbody's Outlook. Does the version of Exchange make a difference? This is an old 2010 version.

[#4]

Go to Active Directory. Go to the properties of the shared mailbox's AD account directly from the OU that it's in.
Go to the Attribute Editor tab of the account.
Find the msExchDelegateListLink attribute and remove any and all users that you don't want to be automapped, from this attribute.
Have the user reboot and reopen Outlook.
You might have to delete and recreate the user's Outlook profile to force the client to let go.