You will need contact your DNS hosting provider and ask them to set your SPF records for you. The SPF record is an open standard specifying a technical method to prevent sender address forgery. More precisely, the current version of SPF – protects the envelope sender address, which is used for the delivery of messages.
"v=spf1 +a +mx +include:spf.email-hosting.net.au ~all"
To authorize an additional mail servers, add the server’s IP address before just before the ~all argument of either of the SPF records above, in the format of ip4:address or ip6:address.
Please note: Multiple SPF records are not recommended and may cause delivery and spam classification issues. If you need to authorise more than one mail server for your domain, we recommend that you update your existing SPF record instead of creating multiple records. This SPF record is for our dedicated email hosting. SPF records for shared hosting will differ.
If you are utilising an Economy, Business or WHM Multi cPanel service, you can modify the MX records set on your domain name by following the steps in this FAQ article.
For more information on SPF records, please read more.