If you do not have the Switch Client for Desktops or Mobiles installed, you have the option to open the Switch Secure Email or Large File online.
To do so, click on the link inside the email to access the Secure Email or package. This will prompt you with a sign-in page asking for your Switch ID and password. After signing in, the Secure Email will then open. Attachments can be opened by simply clicking on them.
There is the option to reply to emails as well, free of charge.