When Sophos lets me know there are messages in quarantine I follow the login link and look at the emails. There is a radio button which allows me to select all the messages and the I can release or release allow or delete and finally delete and block. If I select all and delete and block the messages disappear momentarily then reappear. If I click one messages individually then delete, I get a green box that confirms it has been done and I have do them all individually to clear the list.