Most support ticket tools have the capability to mass-reply to tickets, for the use-case of when there is a mass-issue. This is particularly necessary for any organizations that from time-to-time experience complications, and need to mass reply to all related support requests at once. IE: "Extended Downtime"
Overcoming abuse of functionality
It is understood that the capability to mass-email out of desk could be abused, where other services such as Campaigns would not be utilized. This can be overcome by only allowing a "Mass Reply" feature to be utilized for tickets that are NOT closed, and not allow the creation of new tickets (at least, en masse) for the use of Mass Reply.
Why its important
In one particular case, for one of my clients, they are transitioning from Zendesk to Zoho desk, and would like to let their customers know that there might be some delay in service during the transition. At current, the suggested method from support was to export the list and use Zoho Campaigns. Unfortunately, this is not in alignment with Best Practices.
Related Zendesk functionality