To authorize Bluehornet to send emails on your behalf and authenticate your campaigns you will have to configure it with SPF and DKIM.
SPF
The SPF record mechanism used by Bluehornet is shown below.
include:bluehornet.com
DKIM
Bluehornet offers two types of DKIM hosting solutions. You will have to reach out to your Bluehornet account manager and let them know that you would like to use custom DKIM signing for your domain and they will provide the instructions.
Create a free OnDMARC account to test your configuration.