There's a big downside to using .kz in that the registry has a policy (as per https://nic.kz/rules/ ) that .kz hostnames must relate to "Internet resources" located on hardware and software located within the territory of Kazakhstan. I think the OP is OK as it appears the IP addresses of both the A and MX records are located within Kazakhstan, but something to be aware of if you think registering a .kz is a fun idea(…
Especially given Ive heard some of these TLDs are cheaper to encourage their use, people who want to run services on these should be careful even if enforcement is often lax or nonexistent until a complaint is filed.