Issue in removing another user's mailbox from my profile

Hi,

I've attached another user's mailbox with my mailbox by using this command

Add-MailboxPermission -Identity user1 -User user2 -AccessRights FullAccess -AutoMapping $true

But now I am unable to remove this user's account from my outlook. Whenever I enter this command to remove other user's mailbox from my mailbox

Remove-MailboxPermission -Identity user1 -User user2 -AccessRights FullAccess -InheritanceType All

I am always getting the same message

WARNING: An inherited access control entry has been specified: [Rights: CreateChild, Delete, ReadControl, WriteDacl, WriteOwner, ControlType: Allow]  and was ignored on object "CN=User1,OU=Users=,DC=abc,DC=com".

and I am unable to remove user from my profile.

Can anyone help me  in this regard