Update: this has been resolved as of 11 AM EDT, 3/12/2019
Clicking the link in spam.his.com quarantine notifications in some Browsers (Chrome, Firefox) may take you to a temporary error page. Logging in directly to https://spam.his.com works normally.
We’re working with Barracuda to remedy this. In the meantime, log in directly to https://spam.his.com with your email address and password if you have any problems following the link from your email quarantine notification.