Administrators monitoring XenDesktop have to be logged into Director console or keep checking mails regularly for any possible critical alerts that might affect users of XenDesktop. Instead Desktop Notification Tool notifies the administrators with desktop notifications whenever there is a new alert from any of the numerous sites for which alert policies/alert rules are configured.
Please refer the blog https://www.citrix.com/blogs/2016/01/19/desktop-notification-tool-for-citrix-xendesktop/