In order to receive mail by Hostinger mail server, you need to access your domain DNS zone editor by going to your Control Panel and point your MX record to this address:
Priority Host Points to TTL
10 @ mx2.hostinger.com 14400
5 @ mx1.hostinger.com 14400
Everything should be looking like in the picture below:
NOTE: You can find a detailed tutorial on how to use Hostinger DNS Zone Editor here.