Your DNS Zone can be easily managed with the help of the DNS Zone Editor. You can find it by reaching your control panel, then opening Hosting → Manage:
Scroll down and you will see DNS Zone Editor section:
MX (Mail Exchanger) section provides you with these buttons:
- Button to edit MX record
- Button for deleting your MX record completely
- Button for adding a new MX record
How to add an MX record?
If you are adding MX records for your domain, insert @ as host.
If you are adding MX records for your subdomain, insert the subdomain as a host, for example for subdomain support.hostinger.com you should insert support as a host.