Emails automatically opening up when clicking on inbox or junk folders

I am receiving vast amount of spam emails that are being delivered into my inbox and junk folders partly because the email at the top of the list under Mail automatically opens up when I click on the inbox or junk folders. This is potentially a serious problem because it sends a notification to the spammer that my account is active. I have Outlook webmail installed in which emails do NOT automatically open up when clicking on inbox or junk folders. This unacceptable situation has been doing the rounds for some time and if it cannot be fixed, I will reluctantly have to drop your service.
FYI in mail settings I have ‘mark messages read after displaying for 1 second’ unticked, and ‘mark messages read after opening in separate window’ enabled.