I was able to get it installed on Oracle OS on ARM doing the following, as suggested above.
1.) Initiate an install of Mail Sever
2.) In a terminal, just after initiating run the following command:
sudo sed -i 's/$cpu_arch !=/$cpu_arch ==/g' /www/server/panel/install/mail_sys.sh
3.) Check the install progress. If it failed before the command was run, try again and good luck!