My mom has a 2011 iMac and I want to upgrade it past Sierra to whatever OS is the latest for this Mac. How can this be done? Running the software update option does not bring up Mojave or Catalina so perhaps apple deleted the OS updates for this old mac. Also one other thing I was unable to get Outlook 2011 to work with her email server so had to resort to using apple mail instead. Any ideas? She would prefer Outlook but will use mail instead because it works.