In order to activate the Mail Security relay feature, send an email to the following address: firstname.lastname@example.org . Ask to add the required IP address to Relay.
In your customer Exchange server, setup the following server in the Exchange smart-host "smtp.ateranetworks.com"
In case SPF records is required, add the following record.
"v=spf1 a mx ip4:184.108.40.206/26 ip4:220.127.116.11/24 ip4:18.104.22.168/26 -all"