The issue when you open “Email accounts” in cPanel, it sometimes doesn’t show up the list of Email accounts the domain have but only just a blank page. This happens due to bulk of cache, temp files etc present in the .cpanel directory of domain. You can remove the “.cpanel” directory inside the path /home/cpaneluser/. The issue will be solved.
And don’t worry about the “.cpanel” directory, it will automatically recreate next time when you load the account’s cPanel.