It can be anything! An apex, subdomain, or even a URL.

Results formx.core1.sfdc-ppgy19.mta.salesforce.com

Resolver

Location

A

Name	TTL	Value
mx.core1.sfdc-ppgy19.mta.salesforce.com	300	18.61.9.147AWS EC2 (ap-south-2) / Amazon.com, Inc.
mx.core1.sfdc-ppgy19.mta.salesforce.com	300	18.61.216.216AWS EC2 (ap-south-2) / Amazon.com, Inc.
mx.core1.sfdc-ppgy19.mta.salesforce.com	300	98.130.18.173AWS EC2 (ap-south-2) / Amazon.com