Reply to comment:

Alex Band
When the ticketing system product selection was done, of course IPv6 and security were on the list of criteria. IPv6 support was in the must-have column for a long time, but it competes with other requirements. Of course we could have insisted on IPv6 support, but then we would have ended up with a product that simply doesn't fulfil all the other needs of our users and customers. Let's hope ZenDesk adds IPv6 support soon, we have certainly voiced this to them.