mx2.zeptomail.com has no CNAME records.
Question and response
Question
dig mx2.zeptomail.com. NS
Answer
The response has no answer records.
Authority
zeptomail.com. 2 SOA NS1.ZOHOCORP.COM. dnsadmin.vtitan.com. 2026022203 7200 1800 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0