Thanks for writing in!
You would have to add a new mail server or domain to your SPF records
To enable SPF for your domain, update your TXT record for SPF at your domain provider's management console.
A TXT record for SPF defines the mail servers that are allowed to send mail for your domain. A single domain can have only one TXT record for SPF. However, the TXT record for a domain can specify multiple servers and domains that are allowed to send mail for the domain.
Let me know if you have any more questions, or if you need further help!